Put the kids to bed and have yourself a ball - watching a kiddie TV show aimed at adults. The Secret World of the Very Young (CBS, Wednesday, Sept. 12, 8-9 p.m.) is an electronic exploration of the wonderful, wondrous, often mysterious world of the pre-school youngster. You don't have to be a parent to appreciate this magical hour of joy and bafflement.
Written by David Axelrod and Joe Landon, directed by Sterling Johnson and produced by Tom Griffin, Joe Bacal, and Mark Massari for Sunbow Productions Inc. ,''The Secret World'' is a charmingly unpretentious jigsaw puzzle of a show. It encompasses a variety of colorful pieces made up of sketches, animation, interviews, songs, and lots of fascinatingly talkative talking heads.
Child-behavior experts and stars take part - John Ritter hosts the show, which has recruited such recognizable names as the Smothers Brothers (you know the ''Mom always liked you best'' routine), Joan Lunden, Maurice Sendak, Sally Struthers, Mr. T., and Ruth Gordon. And believe it or not, both Mr. T. and Miss Gordon manage delightfully restrained performances.
But the real stars of the show are the youngsters - hundreds of them at play, in deep thought, commenting on the world around them, alternating sophistication with ingenuousness, just being kids.
Watch ''The Secret World of the Very Young.'' It's a four-star, four-hug show.