Sarah Caldwell, opera's first lady in the adult world, has a philosophy about performing before children's audiences:

"I think children deserve the best performance we can give . . . If we turn on children with good performances, then we cand build audiences for the future."

Caldwell talked about performing for young people yesterday as the Kennedy Center announced its program for the second annual National Children's Arts Festival, opening in Washington April 24 for a one-week stand and then moving to Denver April 29.

Caldwell and Fred Scott will conduct the Opera New England production of the opera version of Mark Twain's short story, "The Celebrated Jumping Frog at Calaveras County."

Often it is the inexperienced performer and makeshift production that is offered to children's audiences. But with artists of Caldwell's stature, the Kennedy Center is trying to enlist first-rate talent for its national children's festival.

Also at the press conference yesterday was Gordon Davidson, who directed Leonard Bernstein's "Mass" and restaged the Pulitzer Prize-winning play, "The Shadow Box." Davison is artistic director of the Mark Taper Forum in Los Angeles. The festival has commissioned a new children's play to be peformed by its Improvisational Theater Project.

The opera cast includes the frog, who races, dances and gets a dose of lead shot; a horse, and a donkey. Caldwell confessed that she loves the puppet animals "almost more than the rest of the cast."

Along with the Mark Twain opera and the new commissioned play, the festival also will highlight the Performing Arts Foundation of Long Island production of "Drums, Whales, and Eskimo Tales" and "We 3," a musical revue tracing the influence of black songs, blues, spirtuals and rag on the American musical theater. It is the joint creation of Leon Bibb, Gail Nelson and Stan Keen.

All events will be free. In addition to performances at the Kennedy Center, traveling troupes will take mini-shows into the schools.

On the opening day of the week-long festival in Washington, there will be a special minifestival for children 3 to 7 years old. Mimes, puppets and clowns will cavort in the Grant Foyer for the youngsters.

A "first" for this second annual festival is the week in Denver as part of the "outreach" policy of the Kennedy Center in its role as a national cultural institution.

Private contributions for the festival came from the McDonald Corp., $50,000; Friends of the Kennedy Center, $310,000, and the Alliance for Arts Education, $30,000.