Glen Echo Park gets a jump on summer fun with its annual Children's Day this Sunday beginning at noon, with clowns, puppets, musicians and more.

You can paint yourself into a giant mural of the park or paint your face. Or you can perform finger puppetry and family folk singing, learn about the 1921 Dentzel carousel and then take a ride on it.

All the following activities are free unless otherwise noted.

OXON HILL FARM -- Open daily, 8:30 to 5, Oxon Hill Road (take Beltway exit 3A, turn right on Oxon Hill Road). Saturday, 11, 12, 2 and 3, sheep shearing. Watch a farmer pull the wool over the sheep's eyes. Sunday, 9:30, help a farmer with the morning chores; meet at the barnyard. 839-1177.

DISCOVERY THEATER -- Tuesday through Friday, 10 and 11:30; Saturday, 1 and 3: Arts and Industries Building, 900 Jefferson Dr. SW. "Just So Stories." The Mermaid Theater of Nova Scotia performs Rudyard Kipling's classic children's tales. $2.50, discounts for families and groups. 357-1500.

CAPITAL CHILDREN'S MUSEUM -- Daily, 10 to 5, 800 Third St. NE. Saturday and Sunday, plant a seed then watch it grow during in spring and summer; materials provided. Sunday, 1 to 5, "Capital Canine Follies." See a celebrity dog show including the animals of diplomats, politicians and athletes. Museum admission, $2. 543-8600.

NATIONAL COLONIAL FARM -- Tuesday through Sunday, 10 to 5, 3400 Bryan Point Rd., Accokeek. Sunday, 1 to 4, Tobacco Planting. 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, Maryland. Saturday, 2, "Trouble at Snowshoe Pass," original puppet show. $2 donation requested from adults. 301/823-2551.

CHILDREN'S RADIO THEATER -- Saturday, 8 a.m., WPFW 89.3 FM. "Nightingale: Part I," a story about a tyrannical emperor who must learn to fall in love within three days. Listeners can participate in a call-in following each program by calling 783-3104.

MAY FAIR -- Friday, 4 to 8, Bethesda, Elementary School, 5011 Moorland Lane, Bethesda. Games, rides, food, bake and plant sale. 496-6339.

PEANUTS PERFORMANCE -- Friday and Saturday, 8, The Odeon, Georgetown Visitation High School, 1524 35th St. NW. "You're a Good Man, Charlie Brown." $4. 966-0969.

BIRDWALKS ON ROOSEVELT ISLAND -- Saturday and Sunday, 8:30, Roosevelt Island parking lot, by the bridge, George Washington Parkway (northbound side only). Bring binoculars, wear subdued clothing. Reservations required. 285-2598.

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 provide. $1 for 20 balls; team reservations. 301/248-4404.

CHILDREN'S PLANETARIUM -- Saturday and Sunday, 1, 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.

SATURDAY MORNING AT THE NATIONAL -- Saturday, 10:30, Western Plaza (across from National Theater); and at 8, Main Stage, National Theater, 1321 Pennsylvania Ave, "The All-American Magic Fest," see 40 of the nation's best magicians. Call 783-3372, 24 hours a day.

SPRING FAIR -- Saturday, 9:30 to 3, St. Bernadette's School, 80 University Blvd. (Four Corners), Silver Spring. Moon walk, flea market, plant sale, games. 593-3268.

KIDS' DOG SHOWS -- Saturday, 10 to 1, Mount Vernon Recreation Center, 2017 Belle View Blvd., (Beltway Exit 1-S bearing south; right on Ft. Hunt Road for 1.5 miles, right on Belle View Boulevard; park entrance immediately to left.); and Saturday, 11 to 1, Mason District Park, 6621 Columbia Pike, Annandale. Enter your dog in one of two shows; categories include best-looking, best- behaved, most-talented, best trick, largest, smallest and best costume. Dogs must be at least six months old, owners four to 14 years old. Register until 10:30 the day of show; $2 per dog. 941-1730 or 768-3222.

MUSICAL OPEN HOUSE -- Saturday, 10 to noon, Levine School of Music, 1690 36th St. NW, third floor. "A Musical Menu," come and see the techniques of learning music; kids three to eight can participate in hands-on music courses and observe special demonstrations and classes. 337-2227.

TRACK AND FIELD MEET -- Saturday, 10:15, Washington-Lee High School, 1300 N. Quincy St., Arlington, "Hershey Track and Field Meet." Kids aged nine to 14 can participate in up to three different events; birth certificate required; registration day of meet from 9 to 9:30. 558-2287.

CHILDREN'S -- Saturday, 11 to 3, Church of the Pilgrims, 22nd and Q streets NW. Entertainment for children, face painting, games, balloons, food and more. 652- 1555 or 653-5303.

MAY FAIR AND AUCTION -- Saturday, 11 to 4, Barnesville School, 21830 Peach Tree Rd. (at corner of Barnesville Road), Barnesville, Md. Pony and hay rides, games, face painting, toys and more. 301/972-0341.

CHILDREN'S CONCERT -- Saturday, 11 and 1, The Barns, Wolf Trap, 1635 Trap Rd., Vienna. Songwriter Cathy Fink with special folk songs for children. $4. 703/938-2404.

INTERNATIONAL FESTIVAL AND CIRCUS -- Saturday, 11 to 4, Queen of Apostles Elementary School, 4409 Sano St., Alexandria. Foods of the world, games, crafts, moonbounce, dunk tank and more; children perform circus acts beginning at 2. 750-3716.

MARET FETE -- Saturday, 11 to 4, Maret School, 3000 Cathedral Ave. NW. Pony rides, moon bounce, international foods, French cafe, white elephant and more. 387-8959.

OLD POST OFFICE -- Saturday, 11:30 to 4, The Pavilion, The Old Post Office, 1100 Pennsylvania Ave. NW. "Just Clowning Around," an afternoon of various entertainment for children: the Town Clowns, 11:30; Primary Movers Dance Company, noon; the dancing Young Americans, 1:30; the ballet and jazz of Accent On Youth, 3. 289-4224.

SPRING GALA -- Saturday, noon to 4, Grace Episcopal Day School, 9411 Connecticut Ave., Kensington. Pony rides, children's movies, raffles, moon bounce and more. 585-3513.

GERMAN SCHOOL FAIR -- Saturday, 1 to 5, The German School, 9440 Newbridge Dr. (off River Road), Potomac. German children's games, entertainment, refreshments and German food. 365-4400.

CHILDREN'S AUTHOR -- Saturday, 1, The Cheshire Cat Bookstore, 5512 Connecticut Ave. NW. Katherine Paterson talks about her books and writing. 244-3956.

MAGIC SHOW -- Saturday, 1 and 2:30, Enchanted Village, Lake Forest Mall, Gaithersburg; Sunday, 1 and 2:30, Enchanted Village, Springfield Mall. "Baffle- O-Bill" entertains with comedy and magic. $3. 301/330-1334 and 703/971-0666.

ADVENTURE THEATER -- Saturday and Sunday, 1:30 and 3:30; special Sunday performance at 5:30, Adventure Theater, "Charlotte's Web." $3, group rates available. 320-5331 weekdays and performance days from 10 to 2.

CHILDREN'S FLEA MARKET -- 10 to 2, Wheaton Park Shopping Center (parking lot), 12009 Georgia Ave., Silver Spring. Browse amongst children's clothing, toys, equipment, books and more. 649-5354 or 598-8955.

INTERNATIONAL FUN FESTIVAL -- Sunday, 11 to 4, 3265 S St. NW (off Wisconsin Ave). Food, entertainment, crafts, balloons, super moon bounce, face painting and more. 462-1317.

CHILDREN'S DAY -- Sunday, noon to 5:30, Glen Echo Park, Glen Echo. "Children's Day," four stages with continuous entertainment (including "Little Red Riding Hood," at 3:30), mural and face painting, and more; puppetry workshop, $1.50; carousel rides for a quarter. 492-6282.

CHILDREN'S ARTS FESTIVAL -- Sunday, 1 to 5, Jewish Community Center, 6125 Montrose Rd., Rockville. Exhibition of children's art, music and dance. 881-0100.