Celebrate Christmas at Hyattsville's Castle Performing Arts Center with special musical matinees for children this Saturday and Sunday. Actors and singers from the University of Maryland will be blending Christmas carols and Broadway tunes. The program is recommended for kindergarteners and up; admission to the show includes free photographs with Santa.

All events are free unless otherwise noted.

NATIONAL ZOO -- Open daily; gates open from 8 to 6; animal buildings, 9 to 4:30. Elephant training demonstrations, 2; Sea lion training demonstrations, 11:30. The Panda house reopens Saturday, although it's still just barely possible that Ling-Ling is great with child; feedings are at 11 and 3. 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-Sunday, 10:30 and 4; help milk a cow, or just see where that stuff they sell in the store comes from. Meet in barnyard. 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. Adults $1; children 50 cents. 377-2825.

CEDAR HILL -- Open daily, 9 to 4, 1411 W St. SE, Anacostia. At Frederick Douglass' home his work is recalled through films, interpretive exhibits and a 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 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; then left on 14th Street and left again on North Market Street and follow the signs. Costumed guides conduct tours of the 1790 mansion. Hands-on exhibits include a loom and spinning wheel and antique toys. Adults $1; under 17, free. 301/694-1646.

CAPITAL CHILDREN'S MUSEUM -- Daily, 10 to 5, 800 Third St. NE. Friday, 10:15; Saturday-Sunday, 1 and 2:30, "Pinocchio." A puppet production of the traditional story. Saturday and Sunday, make a box to hold your favorite belongings. $2; puppet show an additional $2.50. 543-8600.

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

DISCOVERY THEATER -- Tuesday to Friday, 10 and 11:30; Saturday, 1 and 3, in Smithsonian's Arts and Industries Building. Musical "Peter and the Wolf," with shadow puppets, for grades K-4. Adults $3; 12 and under, $2.50; group rates. Information and reservations: 357-1500.

CLOISTERS CHILDREN'S MUSEUM -- Wednesday through Friday, 10 to 4:30; Saturday, 12 to 4, 10440 Falls Rd., Brooklandville, Md. "Little Treasures: Dolls, Toys and Games from the Collection." Films Saturday, 2, "Cicero: the Queen's Drum Horse" and "Angus Lost." $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. Saturday and Sunday, noon to 8, "Old Fashioned Christmas Gardens," an exhibit of trains 'round Christmas trees. The renovated station has a diorama of the trip of Tom Thumb, America's first real passenger train, from Baltimore to Ellicott City. Sound and light shows, model train exhibits and tours. Adults $1.25; under 13, 75 cents. 301/461-1944.

KENNEDY CENTER -- Friday, 7:30; Saturday, 10:30 and 12:30; Sunday, 2; Theater Lab, John F. Kennedy Center for the Performing Arts, "A Christmas Gift From Tomie de Paola," a commissioned play by children's author de Paola based on international folklore. Recommended for children nine through 13. Call 254-3600.

CHILDREN'S RADIO THEATER -- Saturday, 8 a.m., WPFW 89.3 FM. "Cabbage Soup," a variation on the fairy tale "Rapunzel." Listeners can participate in a call-in following each program by calling 783-3104.

SATURDAY MORNING AT THE NATIONAL -- Saturday, 9:30 and 11, Helen Hayes Gallery, National Theater. "Santa Comes to Washington," the Blue Sky Puppet Theater uses puppets, music and singalongs to tell how a disastrous Christmas is averted. Reservations recommended. 783-3372.

DISCOVER THE GALLERY -- Saturday, 10 to 11:30, National Gallery of Art, Fourth and Constitution Avenue NW, "A Christmas Story." For children six to 12. Film "Adoration of the Magi," based on an Italian Renaissance painting; tour of Christmas paintings follows. Free but advance registration required. 842-6249

KIDS' SHOPPING SPREE -- Saturday, 10 to noon, Colvin Run Mill, General Store, (Take Route 7 west from the Beltway five miles). Children may shop for gifts under $5; staff members help kids choose and wrap, while parents just hang around. 759-2771.

CHILDREN'S FILMS -- Saturday, 10, Ramsay Nature Center, 5700 Sanger Ave., Alexandria. "Charlotte's Web" and "The Velveteen Rabbit." Free cocoa. 838-4829.

LONG BRANCH NATURE CENTER -- Saturday, 10 to noon, Long Branch Nature Center, 625 S. Carlin Springs Rd., Arlington, meet with Santa. Saturday and Sunday, 2, see Disney short, "Winnie the Pooh and the Blustery Day." 845-7640.

BALTIMORE AQUARIUM -- Saturday, 11 and 1; Sunday, 2; Pier 3, 501 East Pratt St., Baltimore. Bob Brown with a puppet production of "The Nutcracker." Discussion of puppetry and an aquarium tour follow. $3 members, nonmembers $5. 301/576-3885.

TOYS FOR TOTS -- Saturday, noon to 2, Ole Town Park, Summit and Diamond Avenue, Gaithersburg. Live entertainment; first 150 kids get free photo with Santa; bring a new, unwrapped toy. 926-1184.

OLD POST OFFICE -- Saturday-Sunday, noon to 4, Pavilion, 1100 Pennsylvania Ave. NW. Your picture taken with Santa. $4. 289-4224.

NATIONAL MUSEUM OF AFRICAN ART -- Saturday, 12:30, Auditorium, 318 A St. NE. "Storytime at the Museum in the Oral Tradition," African lore and history, for children of all ages. 287-3490.

SATURDAY STORYTIME -- Saturday, 1:30, Twinbrook Library, Veirs Mill Road and Meadow Hall Drive, Rockville. Stories for children three to six: "Let's Go Shopping" and "New Blue Shoes." 279-1980.

ROUND HOUSE THEATER -- Saturday, 1 and 2:30, Round House Theater, 12210 Bushey Dr., Silver Spring (north on Connecticut, left on Randolph; make second left onto Bushey), "The Enchanted Crane." A multi-media fairy tale including puppets, slides and music; for kids five to 12. $3 per person. Advance purchase recommended. 468-4234.

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, "Comets: Omens or Dirty Snowballs?," for ages seven and up. Latecomers not admitted. 426-6829.

ADVENTURE THEATER -- Saturday and Sunday, 1:30 and 3:30, Adventure Theater, Glen Echo Park, Glen Echo. "Heidi," follow the adventures of a little orphan girl from her home in the Swiss Alps to the big city. $4, group rates available. 320-5331 weekdays and performance days from 10 to 2.

CHRISTMAS PROGRAM -- Saturday, 2 and 3, Cabin John Mall, Atrium, Seven Locks Road and Tuckerman Lane, Potomac, Md. Puppeteering troupe Apuppetsho performs "A Christmas Knight." 279-2526.

TOP OF THE WORLD -- Saturday, 2, World Trade Center, 27th Floor, East Pratt Street, Inner Harbor, Baltimore. "Barry Polisar: Rainbow Morning Music," a live music and magic show; Sunday, 2, magic show for kids of all ages. Adults $1; children five to 15, 75 cents; includes admission to observation deck for view of the city. 301/837-4515.

HOLIDAY MUSICAL CELEBRATION -- Saturday and Sunday, 2, The Castle Theater Performing Arts Center, 5340 Baltimore Ave., Hyattsville. Special children's matinees of popular tunes, traditional carols and dancing. Adults $4, children $3. 277-6121.

CHILDREN'S FILM -- Sunday, hourly from 1 to 4, Springfield Mall and Lakeforest Mall, Gaithersburg. "The Snowman," a British- Academy-Award-winning fantasy about a boy and his snowman. $1. 301/330-1334 and 703/971-0666.