SO YOU'VE just been made Campfire Girls leader/Cub Scout parent/church youth group organizer/playgroup coordinator. Or, between your children and their three friends, you find yourself knee-deep in kids, wondering where to take them.

You'd like to help the impressionable young things take advantage of the many culturally and educationally enriching experiences in this area. You'd also like to get them out of your house. Now what?

There are probably a hundred tours for children's groups in this area, if you include all the business and store owners willing to troop people behind their scenes. If there's a store -- or a firehouse, or a post office -- nearby, you may be able to set something up with a phone call.

Other places to tour aren't always so obvious, and the best ones tend to be quietly guarded secrets of schoolteachers and Scout leaders. We've dug out a handful of these for you, ranging from an onboard train tour to a hands-on tour of Jewish history.

One of the very best -- a surefire hit complete with dogs, horses, policemen and circus tricks -- is given by the U.S. Park Police's Special Forces Branch twice a month, in May, June, September and October. Teachers sign up as much as a year in advance, but there's still room at each remaining demonstration this year, which is how our small contingent got in this month.

Under hundred-foot trees in Rock Creek Park, a huge, dark German shepherd climbs a ladder, paw over paw, and stares at the ring of fire waiting for him at the top. He stares, sniffs and then turns around on the narrow walkway to face his master, Officer Gregory Nester of the U.S. Park Police's Canine Unit.

Jumping through the hoop is the ultimate trick from a bagful that includes such stunts as jumping six-foot walls and crawling through 20-foot tunnels. Teaching the dogs to do battle with walls and fire hoops gives them "confidence," Nester says, and shows the dogs that "we won't ask them do anything they can't do."

He can't do it, or at least he won't do it, at first. The dog looks at his master, turns back to the hoop, turns back to his master, and with a doggy sigh, turns and jumps through the hoop.

The crowd goes wild. Thirty or forty kindergarteners who've signed up for this demonstration from nearby schools shout out, "Yay, Doggie!" and beg to pet him.

Petting comes last, after the children meet all the dogs -- including Black Bart, a Labrador retriever who's addicted to playing fetch with orange balls. The other thing Bart's crazy about is explosives. Bart spends his days sniffing around the White House grounds, hotel ball rooms, parade routes and other VIP hang- outs, seeking the aromatic whiff of a bomb.

The kindergarten kids have a chance to check Bart's prowess. "I've hidden a bomb on one of these vehicles," says Officer James Bartlett, pointing to the lot where we've all parked, "and Bart's going to help us find it." Nervous titters all around. "It's not a real bomb," he hastens to add, "but it smells like a bomb."

"Will it be on your teacher's car?" one mother asks her group. More nervous titters, as Bart puts nose to bumper, tail wagging. The bomb turns up on one of the park police vehicles, to the children's immense disappointment, and Black Bart sits attentively -- waiting for his orange ball reward.

Being an explosives dog is the ultimate in status for the Canine Unit, it seems. All these police dogs, who go home with their officers at night ("I see more of her than I do of my wife," says Nester), go through a 14-week training program -- everything from learning to sit at a hand signal to overcoming the fear of darkness enough to go through a tunnel.

Then they get a break for a couple of months because, says Officer James Lynn, some dogs get tired of training. There then follow another six to eight weeks of explosives training. "That way, if it doesn't work out with the explosives, we can always fall back on the patrol training," he explains.

Also on hand are Officer Leon Gray and his horse Frosty, a team that patrols Georgetown's streets six hours a day. Frosty "can outrun anything up to a Volkswagen," says Gray, and also knows a few fancy steps for the parade grounds. He shows his finest sidesteps and reverse walking -- "something you can't do on a motorcycle," Gray says pointedly.

The animals are definitely the stars of this show and visitors have an opportunity to pet them and ask the police questions. For the kids, it's a very different kind of dog and pony show. CHILDREN'S TOUR CIRCUIT

Here are the details for signing up for the police dog demonstration and a few other tours and demonstrations geared to youngsters. They are free unless otherwise noted.

SPECIAL FORCES ANIMAL DEMONSTRATIONS -- U.S. Park Police, Rock Creek Park. 433-1006. Demonstrations are given the first and third Thursdays of May, June, September and October for groups of 10 to 40. Phone one to two weeks in advance.

AGRICULTURAL TOUR -- Beltsville Agricultural Research Center. 344-2403. Aimed at the older child (fifth grade and up) and adults, the tour highlights research on plants, sheep, dairy and beef cattle, poultry, swine and nutrition. Most of the tour is conducted aboard a bus but, weather permitting, participants may go into the fields and orchards where things like disease-resistant fruit skins are tested. Groups -- which the center defines as "one or more" -- need to sign up one to three weeks in advance. Tours run Monday through Friday.

U.S. BOTANIC GARDEN -- Maryland Avenue and First Street SW. 225-8333. With two weeks' advance warning, you can arrange for an hour tour of the garden's tropical and subtropical plants -- including the two to three hundred orchids in flower each day, and a room tourists have dubbed "The Jungle." There is no lower limit on the number in a group (for older kids sixth grade on up), but very small groups are advised to take the self-guided tour. Tours are Monday through Friday.

B'NAI B'RITH KLUTZNICK MUSEUM -- 1640 Rhode Island Avenue NW. 857-6600. A tour of this museum, whose permanent collection shows the life and religious cycle of Jews, includes a hands-on section where children handle a Menorah, Seder plates, spice boxes and a copy of the Torah. The staff likes two weeks or more advance warning for groups of ten or more from kindergarten age on up. Docents will visit the group in advance if asked, to prepare them for the trip. The tours, which are held Monday through Thursday and Sunday, are free, but there's a suggested 50 cents per person donation.

DALE MUSIC COMPANY -- 840 Georgia Avenue, Silver Spring. 589-1459. This store holds a unique collection of antique musical instruments -- earl Mozart bassoons and clarinets, all kinds of fiddles and cellos, instruments from Africa and the Middle East. Call two weeks in advance for tours on Monday, Tuesday, Thursday or Friday. Groups can range from a handful to about 25.

DULLES AIRPORT -- 471-7838. The airport gives tours Monday through Friday between 10 and noon to kindergarteners on up. The tour includes a short film, a walk through the terminal, and (a great favorite) a ride on the mobile lounge. The staff prefer groups of 10 or more, but no more than 60.

NATIONAL GALLERY OF ART -- Constitution Avenue and Fourth Street NW. 842-6249. Volunteer docents can take preschoolers and older children on special tours of the collection -- everything from the Italian Renaissance to the Christmas Story, with special tours for high school classes in math, science, history and literature. Some tours are given in foreign languages. One program for fifth- graders includes a 40-minute workshop on technique. Call two weeks in advance for reservation. Tours generally run Monday through Friday, but there are occasional weekend offerings. The preferred number in a group is 15 to 30.

UNION STATION -- 50 Massachusetts Avenue NE. 289- 2930. Amtrak Police Officer Art Lawson, alias Officer Choo-Choo, takes groups of children from preschool through sixth grade on a "trip," stopping at the ticket counter, baggage loading and the train where they climb aboard a car (sometimes a private one) and take a look at others. If you request it, Lawson also brings out his puppets for a show on safety. Participants receive various goodies ranging from coloring books to paper hats. Tours are conducted weekdays for 20 to 30 at a time. Give Lawson at least two weeks' notice.

U.S. POSTAL SERVICE -- 8409 Lee Highway, Merrifield, Virginia. 698-6600. Automatic mail sorters, robotic mail movers and behind-the-scenes mail people are featured in this tour of the 51/2-acre facility. Tours for children eight and older are gen Monday through Friday, for about an hour. Minimum number: five. Reserve at least one month in advance.

WOODLAWN PLANTATION -- U.S. 1, Mt. Vernon. 557- 7880. This post-Revolutionary home owned by Nelly Custis Lewis, George Washington's adopted granddaughter, offers tours for everyone from preschoolers to senior citizens. The preschoolers receive a "basket tour," in which a large basket filled with wigs, candles, flax and other items in daily use during Lewis' time are explained and passed. At least one week's warning is required. Tours are Monday to Friday tours; $1 admission for each student, plus $2 per adult supervisor, in groups of 15 to 20.