Kids from all over the United States will perform the rock-musical "Peace Child" this Sunday evening at St. Marks Church in Washington. The presentation of the highly acclaimed show, which premiered at the Kennedy Center in 1982, serves as a dress rehearsal before the group flies to the Soviet Union to perform jointly with Soviet youth. The musical depicts kids of the superpowers who get together to establish peace.

The following activities 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 (Rock Creek Park), 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 and Sunday, 1 to 3, take a free horse-drawn wagon ride; see how a horse is harnessed at 12:30. 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

USS BARRY -- Open daily, 10 to 5, Washington Navy Yard, Ninth and M streets SE. The Navy destroyer's weather deck is open for public viewing and self-guided tours. 433-3377.

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. Friday, 10:30; Saturday, 11, "Puppets on Parade." A variety show of hand, rod and mouth puppets who perform musical numbers. Saturday, 2; Sunday, 3, "Spirit of Magic." Nestor the Magician saws people in half and makes animals disappear from thin air. Museum admission $2; special performances an additional $2. 543-8600.

DOLL'S HOUSE AND TOY MUSEUM -- Tuesday through Saturday, 10 to 5; Sunday, noon to 5, 5236 44th St. NW. Antique dollhouses, dolls, toys, games and an exhibit of antique cat games and toys. Adults $2; under 14, $1; group rates available. 244-0024.

NATIONAL COLONIAL FARM -- Tuesday through Sunday, 10 to 5, 3400 Bryan Point Rd., Accokeek. Sunday, 1 to 4, "Paper Marbling." Farm staff members demonstrate the old art of making marbled paper traditionally used for end papers in books and as covers for stitch books. Admission: 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, Md. "Indian Summer Celebration." Hunt for bear and porcupine hidden in a wall painting, dance around a totem pole, and see an Indian Kachina doll exhibit. Saturday, museum hours, "Indian Crafts." Make tepees, sandpaintings and decorate Indian headbands. $2 donation requested for 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. Demonstrations of agricultural and domestic chores, such as spinning and candlemaking, round out this history lesson. Adults $1; children under 12, 50 cents. Saturday and Sunday, 11 to 4:30, "18th Century Market Fair." See costumed craftsmen and artisans demonstrate and sell their wares; colonial food and music throughout day. 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.

ON WALNEY POND -- Friday, 10 to noon, Visitors Center, Ellanor C. Lawrence Park, Walney Road, Centreville, Va. (I-66 west 11 miles to Rte. 28, make a left, then immediate right on Walney Road; park one mile on left). Kids five and up can join a park naturalist for nature games and activities teaching about aquatic life; bring a fishing pole to try your luck, bait provided. Participants should also bring a small strainer, magnifying glass and boots or shoes for stomping around in the water. 631-0013.

CHILDREN'S RADIO THEATER -- Saturday, 8 a.m., WPFW 89.3 FM. "Clown of God." The story about an Italian juggler who performs a miracle on Christmas. Listeners can participate in a call-in following each program by calling 783-3104.

FISHING TOURNAMENT -- Saturday, 9 to noon; registration from 8:30 to 9, Columbia Island Marina, George Washington Parkway South, Arlington, (take 14th Street Bridge, make first sharp right in direction of Arlington Cemetery onto George Washington Parkway; off ramp bear left, marina is on the left just after bridge). Kids six and older can bring their rods, reels and bait for a chance at hooking bass and other fish; no license necessary. Experts from the Bassmasters will be on hand to help kids out and award prizes. 845-7640.

FUN FAIR AND FASHION SHOW -- Saturday, 9 to 3, Kiddie Korner School, 1609 Great Falls St., McLean, Va., (Rte. 123 south make left on Great Falls Street), "Cystic Fibrosis Fun Fair." Games, bake sale, pony rides, crafts and more; kid's fashion show at noon. 893-6297.

INSECT TREK -- Saturday, 10 to 11:30, Rock Creek Nature Center, 5200 Glover Rd. NW. Join a park naturalist for a walk in search of area insects; appropriate clothing advised. 426-6829.

OLD POST OFFICE -- Saturday, noon to 1, The Pavilion, Old Post Office, 1100 Pennsylvania Ave. NW. The Town Clowns return for more fun and games. 289-4224.

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, Va. (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 are necessary. 255-1827.

NATURE FILM -- Saturday, 11:15, Ramsay Nature Center, 5700 Sanger Ave., Alexandria, "Secrets of the Bee World" and "The Beekeeper." Two films about mother nature's workaholics. 838-4829.

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.

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 young boy who runs off to check out life under the big top. $3, group rates available. 320-5331 weekdays and performance days from 10 to 2.

CHILDREN'S ROCK MUSICAL -- Sunday, 1, St. Marks Church, Third and A streets SE, "Peace Child." Kids from all over the United States perform this rock musical about establishing peace with kids from the Soviet Union. 385-4494.

KIDS' CONCERT -- Sunday, 2 to 3, Walney Visitor Center, Ellanor C. Lawrence Park, Centreville, Va. (Take I-66 west 11 miles to Rte. 28, turn left then immediately right onto Walney Road; park one mile on left), "Romp in the Swamp." Billy B shows you how to do the bog jog and the crab step with a performance of music and comedy. Adults $1; children 50 cents. 631-0013.

STORYTELLING -- Sunday, 2 to 3, Sully Plantation, Sully Road, Chantilly, Va. (take U.S. 50 west to Sully Road; park entrance 3/4 mile on right). Hear Appalachian Folktales and "Jack Tales" from Southern Virginia. Adults $2; children and seniors $1. Price includes admission and tour of the historic house. 437- 1794.