The Kennedy Center Theater Lab, a spacious and high-ceilinged room, was thronged with visitors last night for the opening of its "Black History Month Festival 1982: The Caribbean." The focus of the ongoing exhibition and regularly scheduled performances is on the interconnections between Afro-Caribbeans and Afro-Americans, a theme that surfaced often during the lively performance as well as being graphically apparent in art work decorating the area.

"What we do here is primarily for children," said festival coordinator Jonetta Barras as the session in the Programs for Children and Youth got under way last night. "They become involved in the performance, and that's why we have no chairs." The several hundred who attended -- all but a handful were adults -- were then invited to be seated on the floor.

The lights dimmed and a female folk teller related the story of The Toad and the Donkey as two silhouettes on a white sheet pantomimed the protagonists. Next up was a miniature Afro-Brazilian carnival, a procession of three hoop-skirted revellers accompanied by the "gut rhythm" of two percussionists.

Saved for last was the Big Drum Nation Dance Company of the island of Carriacou, which took the stage to the polyrthymic abandon of rattling chords and a trio of drummers. They provided a startling backdrop to the musical forms we know as blues, gospel and jazz.

Performances are set for Saturdays and Sundays, between 10:30 and 4:30 through February.