WALT DISNEY WORLD, the giant, still-expanding vacation complex built near Orlando by a mouse and dedicated to the young at heart, is celebrating its 10th anniversary this month while its respectful competitors in booming central Florida continue to smile all the way to the bank.

When other outdoor amusement parks take cues from Disney, it's simply good business sense -- the Magic Kingdom that houses Mickey Mouse, Donald Duck and all their friends, and the other slick but inspired elements of Walt's $700 million attraction, have entertained more than 125 million visitors in the last decade to become Florida's biggest tourism success story.

And other entrepreneurs quickly discovered that if you get close enough, some of that success can be catching.

Next October, after an additional investment of more than $800 million, Disney World will open EPCOT (Experimental Prototype Community of Tomorrow) Center's Future World and World Showcase on 550 acres situated two miles south of the Magic Kingdom theme park. If the past is prelude, that blend of foreign government pavilions and pavilions sponsored by major U.S. industries, connected to the park by an extension of the modern monorail, will provide a new boost for the entire state whose tourism receipts this year have been hurt by last winter's freezing weather, high interest rates and economic uncertainty.

To begin to understand the impact of Disney on Florida, you need to consider the magnitude of the "family vacation destination." It is not merely a conglomeratiom of fun rides. Even the word "resort" turns out to be inaccurate, though WDW includes more than one.

In Anaheim, Calif., only 27 miles from downtown Los Angeles, the original Disneyland covers 230 acres. When Walt Disney, master showman and creative dreamer, realized he was boxed in by other people's real estate holdings and thus unable to expand profitably and retain control of his highly commercial fantasies, he and brother Roy made very sure the mistake was not repeated in Florida.

Near the intersection of Interstate 4 and the Florida Turnpike, they bought 27,400 acres (43 square miles -- twice the size of Manhattan), with an estimated value in 1972 of $1 billion. While the theme park (Main Street U.S.A., Adventureland, Frontierland, Fantasyland, Liberty Square and Tomorrowland) is about the same size as its precursor in California, Phase One -- as the initial building project was called -- also includes resort hotels, restaurants, a 450-acre lake, facilities for swimming and boating, golf courses, campgrounds, bridle trails and more, spread over 2,500 acres at Lake Buena Vista.

Water-oriented, surrounded by greenery, free of smog and tinted with Florida sunshine, Walt Disney World greeted those of us who previewed it in October 1971, with music, imagination, color and the fruits of meticulous planning. Since this was obviously one of the most important tourism developments in a decade, it was easy to predict that WDW would become one of the world's major vacation attractions.

But no one could be certain what would be the destiny of the other attractions and areas around the state that depended upon a steady flow of tourists for profit and survival. Apprehensive executives came to visit the massive site that extended into two counties, Orange and Osceola. Disney officials did their best to ladle out soothing comments and allay fears.

"We're not trying to build a wall around Disney World," they said. "There's so much to see in Florida. We know that if people are pleased, they'll come back."

The reassurances proved to be right on the mark. Before WDW arrived, the major central Florida attractions were Busch Gardens, Tampa, in Hillsborough County on the West Coast; Cypress Gardens, 30 minutes south of Disney World at Winter Haven, Polk County; and -- sporadically, depending on the progress of the space program and periodic rocket launches -- the Kennedy Space Center at Cape Canaveral in Brevard County on the East Coast. There also were other attractions, including rolling ranch lands, lakes and the inviting beaches from Clearwater to St. Petersburg to Melbourne.

State tourism figures show that Florida had 23 million visitors the year before WDW opened. In its first year of operation Disney World drew 10 million captivated customers. In 1980, 35.9 million people drove or flew to Florida. And that meant more business for anyone with a good product to sell.

According to company figures, Disney generated more than 52,000 new jobs during the past decade (approximately 21 percent of the work force in central Florida is employed in tourism or related services) and, as of last year, had paid $191.2 million in state and local taxes. WDW itself has from 12,000 to 17,000 employes on the payroll, depending on the season. Visitors to Disney World spent about $14 billion in central Florida from 1970 to '79.

The two major counties involved, Orange and Osceola, saw visitor totals grow from 800,845 in 1970 to nearly 6 1/2 million in 1979, and hotel rooms increased from 5,992 to 31,400 (today there are about 35,000, and a few thousand more rooms will be available when EPCOT opens or shortly after).

Ed Gilbert, state director of tourism, called those counties "the number one destination in Florida" last year in terms of total visitors by automobile and air. Miami, by reason of being an international gateway city, still rated first in air arrivals alone.

Last month, Orlando's new $300-million International Airport opened on 5,000 of 7,000 acres acquired for the City of Orlando by the Airport Authority. Doubling the present 48-gate capacity would require utilization of only another 30 acres of the site, and the city is seeking additional acreage for future runways and noise buffer zones.

The airport "adds a new dimension and gives us a facility that will be able to handle the future number of arrivals predicted," Gilbert said. Other industry officials have noted that travelers from overseas already are responsible for a small but increasing percentage of central Florida visitors, and the jetport will encourage direct flights to the area.

The aggressive efforts by Orlando and central Florida to take a larger share of international arrivals from Miami and south Florida have been described as an escalating battle for tourist dollars. About 6 1/2 million passengers, 350,000 on international flights, used Orlando's airport last year, compared to Miami International's 20.5 million, of which 8.4 million were international passengers.

With a little help from the economy and the weather in coming months, those expected new domestic and foreign arrivals will probably insure that the sweet smell of paid attendance continues to blend with the pleasant aroma of blossoms in the surrounding citrus groves. For central Florida "is still growing," Gilbert added.

Cypress Gardens, with 73 acres developed out of a total of 223, welcomed 1,366,000 visitors last year. It opened two new theme areas at a cost of $5 1/2 million, adding more rides, shops and animal shows to its water ski performances and gardens. The freeze and rising air fares caused a drop in attendance earlier this year, but officials say business is recovering.

Busch Gardens, the Dark Continent, seesawing back and forth with Sea World for the No. 2 attendance spot in recent years, is a 300-acre African-themed "family entertainment center" about 1 1/2-hour's drive from WDW. Featuring rides, shows, and more than 3,000 animals, Busch has long been the most popular West Coast attraction. Camping facilities are available across the street at Busch Gardens Travel Park, and last year Busch built its 22-acre water theme park, Adventure Island. (Busch also operates Busch Gardens, Williamsburg and Sesame Place in Bucks County, Pa.)

Attendance in 1980 was 3.1 million, making it the sixth straight record year. Officials say business is now rebounding after a bad winter start.

Sea World, which followed Disney to Orlando in 1973, consists of a $40-million investment covering 250 acres only 10 minutes east of WDW and billed as the world's largest marine life park. It offers six major shows and 21 exhibits, with performing marine animals. The star is Shamu, an 8,000-pound black-and-white trained killer whale.

Last year, a $5-million Shark Encounter facility opened, featuring a 600,000-gallon enclosed aquarium and a moving sidewalk inside a nine-foot-high acrylic tunnel that allows visitors to walk safely along the bottom of the aquarium "among" the sharks. Florida Festival, a $7-million shopping and dining complex, opened in late 1979. Among future projects are Cap'n Kid's World, a two-acre water-themed play area, which is scheduled to open at the end of this year.

Attendance in 1980 also topped 3 million, and a spokesman said it is now running nearly 4 percent over the same period last year.

Circus World arrived next, in February 1974, 25 minutes southwest of Orlando and 10 minutes from Disney, in Polk County. Ringling Bros. and Barnum & Bailey's colorful and evocative production spreads the sights and sounds of the circus over 110 acres, featuring the three-ring "Circus Spectacular" and other attractions and shops. This year new thrill rides and shows have been added, including David McMillan's Flying Tiger Act. There are 740 acres held for future expansion, with 225 acres in citrus groves.

Next summer the first phase of Little England will open near the entrance to Disney World on 294 acres, one quarter of the available land.

In 1984, Music Corporation of America Inc. is scheduled to open Universal City, Fla., a $170-million attraction 15 minutes from WDW. Patterned after the Universal City tour operation in L.A., it will feature "sets, shows and demonstrations" and a modern motion picture-TV studio that should prove a boost to the Florida film industry.

But the last word still belongs to the Disney organization.

Disney World attendance also suffered as a result of the problems that beset Florida this year, including the bad publicity about crime in Miami, but officials were expecting the fourth quarter that ended last month to show a decline of only 3.8 percent from last year's total of 13.8 million vacationers. International arrivals, many from Canada, make up about 10 percent of Disney's attendance, a spokesman said. "It's our growth market." But most foreign travelers "don't realize we're 300 miles from Miami."

Still, Disney officials predict, one year after EPCOT Center opens its gates on Oct. 1, 1982, total annual WDW attendance will have reached a record 22 million visitors. And what will they see at EPCOT?

Aside from more rides and more shops, the project will feature two main themed areas. The first, Future World, spotlighted by a 17-story-high geodesic sphere called Spaceship Earth, will house six pavilions on 120 acres devoted to energy, land and transportation. Sponsors include the Bell System, Exxon, General Motors, Eastman Kodak, Sperry Univac, General Electric, Time Inc., and Kraft. At least two additional pavilions will be built later.

The second theme area is World Showcase, which will feature international pavilions in the "Community of Nations," where the history, culture and food of many lands will be presented on 140 acres (the site includes a 40-acre lake). American Express and Coca-Cola will jointly sponsor the host pavilion, "The American Adventure."

Eight international pavilions -- Mexico, Italy, Germany, the United Kingdom, France, Canada, Japan and the People's Republic of China -- are expected to be ready on opening day. Though none are presently receiving financial support from their governments, corporate funds are being supplied in all cases except China. However, all governments are cooperating in the projects, WDW officials say, and China has permitted Disney film crews to record "never-before-seen subjects."

Those who can't wait until next fall should visit the Preview Center on Main Street and view a film about EPCOT. If you've never been to Disney World before, take a few days to look around and you'll have no doubt about its impact. As everybody knows, if you build a better mousetrap