Cartoon hero Mickey Mouse steps off the Disney jet for a Washington appearance Friday at the Woodward and Lothrop store downtown. He'll emcee a live stage show featuring characters from the soon-to-be-released animated Disney film "The Black Cauldron." Later in the afternoon, you can meet Mick and give him the grip.

Or perhaps you'll want to pull your head out of the sand this weekend to see the newly hatched ostrich triplets at Pet Farm Park in Vienna. They're sprouting at a rate of one foot a month, so you'd better make tracks. And as long as you're there, you might as well hop on a 100-year- old tortoise or pet a llama.

All the following events are free unless otherwise noted.

NATIONAL ZOO -- Open daily; gates open from 8 to 8; animal buildings, 9 to 6; panda feedings, 11 and 3; elephant training demonstrations, 2; sea lion training demonstrations, 2, 3001 Connecticut Ave. NW, on the Metro Red Line. Family learning centers Zoolab and Birdlab open Friday through Sunday, noon to 3; Herplab open Wednesday through Sunday, noon to 3. 673- 4717.

OXON HILL FARM -- Open daily, 8:30 to 5, Oxon Hill Road (take Beltway exit 3A, turn right on Oxon Hill Road). Saturday, 9, "Morning Chores." Help a farmer milk the cow and feed the animals. Sunday, 2, "Horse Sense." Learn all about horses. 839-1177.

NATIONAL AQUARIUM -- Open daily, 9 to 5, Department of Commerce, 14th and Constitution Avenue NW. The sharks are fed Monday, Wednesday and Saturday at 2; weekday features are a touch-tank, mini- theater and a thousand types of marine life. School groups should schedule in advance. Adults $1; children 50 cents. 377-2825.

CEDAR HILL -- Open daily, 9 to 4, 1411 W St. SE, Anacostia. Cedar Hill, Frederick Douglass' home, recalls his work with films, interpretive exhibits and a house tour. 426- 5961 or 426-5962 or 426-5963.

PETTING ZOO -- Weekdays, 10 to 5; weekends 10 to 7, Pet Farm Park, 1228 Hunter Mill Rd., Vienna. Exotic animals from around the world come within arm's reach. Adults $4; under 13, $3.50 (admission includes guided tour, hay ride and animal food. 759-3636.

CHILDREN'S MUSEUM -- Monday through Saturday, 10 to 4, Sunday 1 to 4, Rose Hill Children's Museum north of Frederick. Take U.S. 15 north to Exit 8 to Motter Avenue; follow Motter to left onto 14th Street and left onto North Market Street, follow signs to Rose Hill. Costumed tour guides conduct tours of the 1790 mansion. Hands-on exhibits include a loom, antique toys and spinning wheel. Adults $1; under 17 free. 301/694- 1646.

CAPITAL CHILDREN'S MUSEUM -- Daily, 10 to 5, 800 Third St. NE. Saturday, 2; Sunday, 3, "Nestor the Magician" is back to make animals disappear into thin air; $2 to see the show only; $3.50 to see the show and the museum. Regular museum admission, 2. 543-8600.

DOLL'S HOUSE & TOY MUSEUM -- Tuesday through Saturday, 10 to 5; Sunday, noon to 5, 5236 44th St. NW. A collection of antique dollhouses, dolls, toys, games and an exhibit of antique cat games and toys. Adults $2; under

NATIONAL COLONIAL FARM -- Tuesday through Sunday, 10 to 5, 3400 Bryan Point Rd., Accokeek, "Wheat: Harvest to Oven." See the grain travel from field to table. Adults $1; children under 12, free. 301/283-2113.

CLOISTERS CHILDREN'S MUSEUM -- Wednesday through Friday, 10 to 4:30; Saturday, 12 to 4, 10440 Falls Rd., Brooklandville. "Indian Summer Celebration." Hunt bear and porcupine hidden along a nature trail, dance around a totem pole and see an extensive Kachina doll exhibit. Saturday, museum hours, "Indian Crafts": make tepees, sandpaintings and decorate Indian headbands. $2 donation requested from adults; group tours available. 301/823-2551.

RAILROAD STATION MUSEUM -- Wednesday through Saturday, 11 to 4; Sunday, noon to 5, Main Street and Maryland Avenue, Ellicott City. The renovated station has a diorama of the trip of Tom Thumb (an early 19th-century train) from Baltimore to Ellicott City. There are also sight and sound shows, model train exhibits and tours of the museum. Adults $1.25; under 13, 75 cents. 301/461-1944.

COLONIAL FARM -- Wednesday through Sunday, 10 to 4:30, Claude Moore Colonial Farm at Turkey Run, 6310 Old Georgetown Pike, McLean. Take a self-guided tour of farm life for a low-income family in Colonial Virginia. Ongoing demonstrations of agricultural and domestic chores, such as spinning and candlemaking, round out this history lesson. Adults $1; children under 12, 50 cents. 703/442-7557.

ANACOSTIA NEIGHBORHOOD MUSEUM -- Friday 10 to 6; Saturday and Sunday, 1 to 6, 2405 Martin Luther King Jr. Ave. SE. Afro- American history lectures to ages four through eight as well as group tours and teaching services. 287-3369.

MICKEY MOUSE LIVE -- Friday, noon, Woodward and Lothrop, Sportswear Department, 11th and F Street, "The Black Cauldron." Mickey Mouse hosts a live stage show based on this latest animated Disney film. From 2 to 3 meet Mickey in the children's department. $3. 879-8752.

CHILDREN'S MUSICAL THEATER -- Friday and Saturday, 7:30, Auditorium, John Eaton Elementary School, 34th and Lowell streets NW, "Guys and Dolls." 60 students aged eight to 16 perform this Broadway hit in Cleveland Park's annual summer production. $3. 362-8247.

CHILDREN'S RADIO THEATER -- Saturday, 8 a.m., WPFW 89.3 FM. "Nana Upstairs, Nana Downstairs," the story of visiting grandma. Listeners can participate in a call-in following each program by calling 783-3104.

CHILD SAFETY DAY -- Saturday, 9 to 3, Reston Community Center, 2310 Colts Neck Rd., Reston. "Child Safety Day." Police and others help parents put together a free "Identi-Kid" package for each of their children; the kit includes vital statistics, dental charts and photographic and fingerprint records; special events throughout the day, including appearances by cartoon characters and McGruff the crime dog. 476- 4500.

BATTING PRACTICE -- Saturday, 10 to 3; Sunday, 1:30 to 4:30; Tuesday and Thursday, 3 to 7:30, Tucker Road Community Park, 1771 Tucker Rd., Fort Washington, Md. Batting cage and automatic pitching machine; bats, balls and helmets provided. $1 for 20 balls; team reservations. 301/248-4404.

CHILDREN'S OPERA -- Saturday, 11, Wolf Trap Farm Park for the Performing Arts, 1624 Trap Rd., Vienna. (Take Rte. 7 west from the Capital Beltway for 21/2 miles and turn left at Towlston Road, at the brown Wolf Trap directional sign), "Fluerette." A special one-act opera for kids based on Offenbach's comic operetta. Free, but advance reservations necessary. 255-1827.

INSECT WORLD -- Saturday, 11, Ramsay Nature Center, 5700 Sanger Ave., Alexandria. Join an entomology expert for an introduction into the world of insects; children under 10 must be accompanied by parents. 383-4829.

TROLLEY MUSEUM -- Saturday and Sunday, noon to 5, Northwest Branch Regional Park, Bonifant Road between Layhill Road and New Hampshire Avenue, north of Wheaton. Trolley rides: $1 adults; under 18, 75 cents; under two, free. 384-9797.

CELEBRATION -- Saturday, noon to 4, Wheaton Regional Park, 2000 Shorefield Rd. (off Georgia Avenue), Silver Spring, "National Therapeutic Recreation Week." Cloggers, games, music and entertainment from Kids on the Block. 496-9477.

FUN FAIR -- Saturday, 1 to 5, Chinquapin Park, 3210 King St., Alexandria. A day of family folkdancing, face painting, juggling, magic and more; magician Myklar the Ordinary performs at 1. 838-4343.

CHILDREN'S PLANETARIUM -- Saturday and Sunday, 1 and 4, Rock Creek Nature Center, 5200 Glover Rd. NW. First show for children four to seven (must be accompanied by an adult); second show for ages seven and up. No latecomers are admitted. 426-6829.

ADVENTURE THEATER -- Saturday and Sunday, 1:30 and 3:30, Adventure Theater, Glen Echo Park, Glen Echo."Toby Tyler," the story of a boy who runs off with the circus to check out life under the big top. $3, group rates available. 320-5331 weekdays and performance days from 10 to 2.

ALL ABOARD -- Sunday, 1 to 3, Burke Lake Park, 7315 Ox Rd., Burke. (I-66 west to Rte. 123 south, which becomes Ox Road). Take a 15-minute ride through the woods on a miniature train to learn about forest life. 50 cents per person (non-county residents must pay $3.50 park entrance fee). 451-9588.

PUPPETS IN THE PARK -- Sunday, 7 to 7:45, Newton Edwards Amphitheater, Mason District Park, 6621 Columbia Pike, Annandale. From the Beltway take Rte. 236 east two miles; make left on Columbia Pike, park entrance on right. 941-1065.