ONE TO TACKLE The 34th annual Fishing Rodeo for kids is 10 to 1 Saturday at the Battie Mixon Pond on the C&O Canal in Old Town, Maryland, 10 miles south of Cumberland. Soon-to-be-fishing-champs 15 and under can bring their tackle to the pond, which will be stocked with more than 500 of the aforementioned bewhiskered beauties. Free. 301/759-6440.

WARM WEATHER NOTES Put some music in your life with the following concerts, all free:

The prodigies of the National Symphony Orchestra Summer Youth Ensemble toot their horns and pluck their strings to the scores of Beethoven, Rossini and Mozart at 8 Friday in the Kennedy Center Theater Lab. Call 254-3600.

Pair a picnic with the light classical fare of the Monumental Brass Quintet 5 to 7 Sunday at the Village Center, Walker Road and Georgetown Pike in Great Falls, Virginia. 451-4492.

The U.S. Air Force Band and Singing Sergeants bring selections from "Fiddler on the Roof" and other uplifting tunes to the Sylvan Theater at 8 Friday. Call 767-5658.

Art and music come together at 7 Sunday when the Bowdoin Trio plays works by Schubert and Schoenberg in the Garden Court of the National Gallery of Art. Call 737-4215. LIMBERING UP The Sokol gymnastics tradition was begun in Czechoslovakia 125 years ago to create "a complete man." See how far they've come at the 20th Sokol USA Slet and National Gymnastic Championship 7:30 Saturday at the D.C. Armory, 2001 East Capitol St. Besides individual routines, Olympic gold medalist Jim Hartung and 500 gymnasts, ages 11 to 60, will perform mass calisthenics. Tickets are $10, $5 for kids under 10. Call 547-9077 for details, 432-0200 to charge tickets.

THE FESTIVAL OF AMERICAN FOLKLIFE A Washington tradition, this year's Smithsonian Festival of American Folklife on the Mall runs (on and off) through July 5. Here are some highlights:

More than 90 participants from Michigan celebrate the state's sesquicentennial with Afro-American gospel, old-time fiddling and Finnish-American music. On the food front Michiganders will cook up muskrat, and smoked fish and meat and vegetable pasties will be for sale. Exhibitions on the Great Lakes waterways will cover fishing and river culture, and trappers will detail life in the backwoods.

"Cultural Conservation: America's Many Voices" focuses on the nation's multilingual heritage with music, oratory, crafts, games and rituals. Mexican-Americans from Laredo, Texas will make saddles, quilts and toys and a baracoa will barbecue. Chinese-Americans from New York City will demonstrate calligraphy, games and the occupational folklore of restaurant workers while Lao-Americans celebrate their Rocket Festival, traditionally used to encourage rain, beginning at 11 Sunday.

Washington musicmakers climb onto the folklife stage in a program that includes local bands, choirs and soloists performing gospel, blues, salsa, reggae, go-go, Chinese Opera and more, all in front of the Museum of Natural History.

All events are free on the Mall, between 12th and 14th streets, 11 to 5:30 Friday through Sunday and then again July 1 through July 5. Every night 5:30 to 7 (except July 4) there'll also be free dance parties led by festival artists. Pick up a schedule at the festival. Take Metro's Blue/Orange Line to the Smithsonian station. Call 357-4574.

SUPER EXHIBIT Since leaping his first tall building in 1938, Superman has been a powerful crime- stopper, at least in millions of comic books and the TV, movie and stage productions that have starred the hero from Krypton. The Smithsonian National Museum of American History now brings us "Superman: Many Lives, Many Worlds," an exhibition of 50 years of posters, scripts and even the costume from the upcoming "Superman IV" movie. The museum's at 14th and Constitution NW. 357-2700.

ARTS AWHIRL Tap your child's talents this week at Kaleidoscope, a free arts workshop in a tent, with 19 different stations where kids can paint with melted crayons, make jigsaw puzzles, play calypso music, make masks and more. It's for kids 6 to 12 at Glen Echo Park, on the hour from 9 to 3 Saturday and 1 to 3 Sunday. Pick up tickets 30 minutes before each session. Continues Monday and Tuesday; call 232-5877.

TRADEMARK LARKS Trademark Expo '87 brings familiar faces to town 9 to 5 Saturday and Sunday at the National Tourist Information Center in the Commerce building, including Tony the Tiger, a 30-foot inflatable American Tourister gorilla and even a couple of larger-than-life M&Ms. Consumer exhibits and manufacturer's samples will be available. It's free at 1400 Pennsylvania Ave. NW. Call 557-3341.

TRADEMARK LARKS Trademark Expo '87 brings familiar faces to town 9 to 5 Saturday and Sunday at the National Tourist Information Center in the Commerce department, including Tony the Tiger, a 30-foot inflatable American Tourister gorilla and even a couple of larger-than-life M&Ms. Consumer exhibits and manufacturer's samples will be available. It's free at 1400 Pennsylvania Ave. NW. Call 557-3341.

ALIGHTING TRADITIONS If you're looking for something traditional and unusual, bring a picnic and join the Polish American Arts Association on the steps of the Lincoln Memorial to celebrate the Wianki Festival of Wreaths 6 to 10 Saturday evening. After a program of traditional Polish dance and music, visitors can make candle-topped wreaths and cast them on the Reflecting Pool. Free. Call 656-3592.

REST OF THE BEST The Next Step AIDS 10K Walk starts at 9 Sunday at the Sylvan Theater and includes lunch at Tracks nightclub. It's $15 or get a sponsor sheet at 628-4164 . . . Dates with local notables will be auctioned at the Bachelor/Bachelorette Bid to raise money for the March of Dimes at 6 Friday at the Sheraton Grand, 525 New Jersey Ave. $10. 824-0111 . . . The Washington Soap Box Derby trial runs are 9:30 to 3 Saturday in the 6500 block of 26th street, between Underwood and Sycamore streets, in Arlington. 279-7174.