Each year's birthday, as every mother knows, is The Most Important one for a child, once they get past the stage when they have to eat their vegetables.

What could be more fun than celebrating with magicians and clowns? Unless, of course, they've been to the neighborhood so many times that children know the tricks by heart and the clowns by name.

Imagine the face of an 8-year-old discovering a giant Moon Bounce in his back yard. Or that of a 2-year-old riding a pony around his favorite tree. Most 13-year-olds would love a hayride on a moonlit night, followed by a giant bonfire. And who'll ever forget a big brother's dance party -- the night the house was filled with '50s music and bobby sox?

If budget is a consideration, remember that you don't have to break the bank to give a child a great day. A nature walk along the C&O Canal followed by a picnic in the grass is not only educational, but a great way for small boys to vent their energies.

A scavenger hunt with a good list can take up most of the afternoon, and a fishing trip could provide a real sense of accomplishment.

Here are 101 ways (in alphabetical order) to celebrate Most Important Birthdays: enough to keep you going into the time you're planning parties for grandchildren.

HOME HAPPENINGS (For a charge)

Acting Workshop: Real, live actors come to your house: Fairfax County Council of the Arts (941-6066, fees vary).

Balloon Delivery: Amusements Unlimited, dispatched by a gorilla or giant chicken (593-2900, $40 for 2 dozen).

Balloon Sculpture: Amusements Unlimited ($50 an hour); Creative Parties (770-1550, $75 an hour and up); Carroll the Magician (532-8181, $35 and up), and others.

Birthday Baker: Beverly Kobrinetz teaches children to make bread sculptures (460-3191, $5 per child).

Caricaturists: Amusements Unlimited (2-hour minimum, $75 per hour); Creative Parties ($75 and up).

Clowns: Wayne Alan Magical Productions, Ltd. (779-2655, $65); Amusements Unlimited ($50 and up); Lollypop the Clown with Aladdin the Magician (439-1516, $50 per performer); Bob Freed Productions (737-4713, $75 and up)

Computer Pictures on Clothing: Creative Parties ($275 minimum, 4 hours).

Dance Instruction: Fairfax County Council of the Arts (fees vary).

Eastern Onion: Birthday messages delivered by character of choice. ($35 and up; $7 travel fee outside of D.C., 984-3200).

Face Paintings: The Wonder Co. (966-9777, $55 for 1, $100 for 2); 11-year-old assistants help through Mar-Va-Teen, Rockville. Call Alice Krindler 951-0635; or have children paint each others' faces.

Instrumental & Singers: Fairfax County Council of the Arts (fees vary).

Juke Box Dance Party: Amusements Unlimited ($150 per evening. Programmed to decade of choice).

Magicians: Wayne Alan Magical Productions, Ltd. ($65); Amusements Unlimited ($50 and up); Aladdin the Magician with Lollypop the Clown ($50 per performer); Creative Parties ($75 and up); Carroll the Magician ($35 and up); Christian the Magician (768-7268, $50 and up); Dubow the Magician of Al's Magic Shop (789-2800, $50 and up); Bob Freed Productions ($50 and up); Fairfax County Council of the Arts (fees vary).

Merry-Go-Round: A & A Bernies Kiddie Ride Rentals (323-0147, $65 an hour).

Mimes: The Wonder Co. ($55 for 1, $100 for 2); Amusements Unlimited ($50 and up); Fairfax County Council of the Arts (fees vary).

Moon Bounce: A & A Bernies Kiddie Ride Rentals ($75 for 1 hour); Amusements Unlimited ($150 and up for 3-hour parties).

Movies: Amusements Unlimited ($60 for two, 20-minute shorts with cartoons). Check local libraries.

Pinatas: Mixtec, Columbia Rd. & 18th St. NW.

Pin Ball Machines: Amusements Unlimited ($150 for evening); Creative Parties ($150 per party).

Pony rentals: A & A Bernies Kiddie Ride Rental ($75, two ponies for 1 hour); Brandywine Stables (372-8914, $10 per hour from time leaving stables to return; transportation for ponies not provided).

Puppet Show: Wayne Alan Productions ($65); Amusements Unlimited ($75); Creative Parties ($75 and up); Bob Freed Productions ($75 and up); Fairfax County Council of the Arts (fees vary).

Story Tellers: Bob Freed Productions ($75 and up); Fairfax County Council of the Arts (fees vary) or Jon Spelman (797-8399) and Mark Spiegel (797-1036).

Video Games: Amusements Unlimited ($150 for evening).

Ventriloquist: Wayne Alan Productions, ($65).

Free

Acting: Make up a play or have a short play selected for children to act out. While dress-up is not necessary, it's fun.

Blind man's bluff.

Blown-up balloons to take home.

Decorated goody bags: Use sandwich-sized bags, glue, sparkles, colored stars, etc. Spell name with glue and sprinkle sparkles over.

Charades.

Table Art: Have children decorate paper place mats and tablecloths with crayons.

Great XXXXX Day. Pick child's idol or select a person your child would admire who was born on or near his birthday. Read biography, if available, and let the child dress up and be him or her for a day.

Hobby theme party.

Reverse Luncheon: First course, dessert (ice cream and cake, of course); second course, hamburgers or sandwiches.

Mad Hatters Tea Party: Put a bunch of old clothes in a chest or box. Let children dress up, then have a tea party. Serve peanut butter & jelly sandwiches (quartered in triangles), lemonade (in tea cups), M&M's (in nut bowls).

Create-Your-Own Lunch: Have younger children concoct combinations and designs with carrot sticks, celery, peanut butter, raisins, and whatever else sounds creative.

Make-it-yourself ice-cream sodas: Provide cherries, nuts, soda, syrups, canned toppings.

Mock wedding: This takes someone who likes to sew and make costumes. If you don't want to marry the children, marry the neighborhood dogs and dress children as "invited guests."

Paint your own T-Shirt.

Pajama parties.

Pin the Tail on the Donkey.

Scavenger Hunt: Make up a list of hard-to-find items (examples: hair pins, stick matches, 12-ounce coke bottle, gold safety pin). Split the group into pairs. Send them out into the neighborhood to knock on doors and collect items (no more than 10). First team back wins the prize.

Toy Fantasia: While child is asleep, hang from the ceiling model airplanes, dolls, balloons, etc., for a special birthday morning wake-up.

Treasure Hunt: Hunt for pennies, peanuts (watch out for squirrels) or candy hidden in yard.

Wall Drawing: Cover a large wall with paper, have guests and birthday celebrant write and draw on it, roll up at end and save for the 21st birthday.

Window Painting: Decorate and paint windows with watercolor paints.

AWAY FROM HOME

Apple- and berry-picking. Call County Extension services.

Arboretum.

Arcades.

Audubon Naturalist Society, Bethesda: 652-3810. Bird-watching walks.

Baseball games, county softball games, polo matches on mall.

Boat rental in Annapolis.

Bowling.

Cabin John Regional Park: small zoo and picnic area, 565-74l7.

Camping.

D.C. Department of Recreation, 629-7226.

Fishing ponds.

Fire House Tours: Call local station to arrange visit.

Glen Echo Park: 320-5331. Adventure Theatre, adult productions for children, usually weekends.

Go-kart racing.

Harpers Ferry, for a ride on Old Time Steam Train.

Hall of Musical Instruments, National Museum of American History.

Hayrides: Brandywine Stables, Branch Ave. at Rte. 5, Brandywine, Md. (372-8914, $4 per person, $100 minimum. Includes bonfire).

Horseback riding: Brandywine Stables, 372-8914, $8 per hour weekdays, $10 per hour weekends; Rock Creek park and others. Check Yellow Pages.

Ice Cream Parlors.

Indoor Ice Skating (Lake Forest Mall and Tyson's Corner).

Kennedy Center Programs, 872-0466.

Kenilworth Aquatic Gardens, 426-6930.

Kite-flying.

Library of Congress.

Library Theater, 426-7734.

Lincoln Memorial. (Call Department of Interior, 426-6842.)

McDonalds for lunch.

Movies: American Film Institute, Kennedy Center, children's matinees, local theaters.

Merry Go Round, on the mall.

Miniature golf.

Montgomery County Department of Recreation, Bethesda, 468-4176.

Prince George's County Department of Recreation, 227-2200.

Moon Bounce.

Movies.

National Capital Children's Museum (computers to play on, metric room, city room, several exhibits; party facilities available in Washington, 543-8600).

National Capital Parks: 426-6975. (Dial-a-park, for daily breakdown of park activities anywhere.)

Nature walks: Theodore Roosevelt Island 426-6922; Arlington Co. Long Branch Nature Center 671-7716; Gulf Branch Nature Center 558-2340; Brookside Nature Center Wheaton 946-9071; Fort Dupont Activity Center, 426-7723; C&O Canal; Appalacian Trail.

National Zoo.

Pet-a-Pet Farm, Hunter Mill Road, Reston.

Picnics.

Planetarium, Rock Creek Park: Shows during day.

Pool Hall. (Call local centers to see if rentable.)

Puppet Show: The Grand Centennial Puppet show, 38l-5395.

Roller skating.

Skate board rink.

Smithsonian Insect Zoo.

Smithsonian Puppet Theater, Crafts & Sciences, History 381-6722

Swimming party.

Trolley Museum (Bonifant Rd. off Layhill Rd., Wheaton, 384-9797).

Washington Doll's House & Toy Museum: Party refreshments and entertainment available, 244-0024).

Turkey Run Farm.

Wheaton Regional Park, 946-9071.

Whites Ferry, Poolesville, Va.: Car ferry to Leesburg across Potomac River.

White-water rafting.

Wilson Line (ride on the Potomac).

Wolf Trap Farm Park, Summer Interpretive Program, call for scheduling, 281-5587).