Two poignant and probing books on growing up in Hollywood Twinkle, Twinkle, Little Star, by Dick Moore. New York: Harper & Row. Illustrated. 303 pp. $16.95. Hollywood Dynasties, by Stephen Farber and Marc Green. New York: Delilah Communications. Illustrated. 365 pp. $16.95.

In every teen-ager's life there is that moment of truth when one has to kiss a person of the opposite sex for the first time. It can be an awkward moment, as the gangliness of adolescence joins forces with the inexperience of youth.

For child star Dickie Moore, the first time he kissed a girl at age 16 was especially awkward. It was a scene in the movie ''Miss Annie Rooney,'' which meant he would have to do it in front of most of the cast and crew. To make matters worse, his ''date'' in the scene was none other than Shirley Temple, then an adolescent herself and about to receive her first screen kiss. This meant that Dickie's moment of truth was also going to be recorded by the world's press.

In ''Twinkle, Twinkle, Little Star,'' Dick Moore looks back at growing up in Hollywood, recounting his own experiences as well as interviewing such child stars as Shirley Temple Black, Donald O'Connor, Jane Withers, and Roddy McDowell. The book appears to be an act of catharsis for Moore and for many of the people he spoke to as well.

We get many painful stories, as one would expect in a volume like this. Much of it has been softened, since it is Moore writing about himself and his peers. Moore recounts how child star Jackie Coogan grew up to find that all the money he had earned had been spent or gambled away by his mother and stepfather. Coogan also tells Moore how Charlie Chaplin, who made Coogan a star in his film ''The Kid,'' gave him $10,000 in cash when Chaplin discovered he was broke.

''Chaplin was a real friend, the only person I could count on,'' said Coogan.

Moore's book is divided by subject matter so that we get glimpses of family life, schooling, and how the big names of Hollywood interacted with children. Spencer Tracy's reputation as a thorough professional is further enhanced by Sidney Miller, who worked with him in ''Men of Boys' Town.''

''A lot of stars wouldn't stay on the set when your close-up was being shot, '' relates Miller, ''but he would.'' Tracy had an effect on more than one young actor. Bobs Watson told Moore how working with Tracy influenced his subsequent career in the ministry.

If ''Twinkle, Twinkle, Little Star'' is not the definitive book on the subject of child performers, it is a useful compendium of anecdotal material. The performers who spoke to Moore, some in their last public interviews, were talking to a peer who could empathize with what they had gone through. In the end one gets the impression that in spite of the difficulties it was an experience most of them wouldn't give up for the world.

Stephen Farber and Marc Green consider a different aspect of growing up in Hollywood in their book ''Hollywood Dynasties.'' Their concern is not with child stars, but children of the stars, particularly those children of famous moviemakers who follow in their parents' footsteps. Such families as the Coppolas, the Ladds, and the Mankiewiczes are examined in magazine-length profiles. Most of the stories seem to reach the same conclusion: Carrying a famous family name is difficult, but if you're trying to make it in Hollywood, it doesn't hurt.

The book is not intended to be a collection of gossip, and the seriousness of the research and the extensiveness of the interviews are apparent. Nonetheless, as a collection of private family histories, it can often make the reader feel intrusive. Learning that Jane Fonda and Peter Fonda both learned of their mother's suicide, not from their father but from accidentally reading about it in a magazine, one is apt to be embarrassed that something so painfully private is on display.

The stories are not all grim. For every episode of family strife, such as Darryl Zanuck having his son Richard dismissed from Twentieth Century-Fox, there is a moment of family pride, as when actor Kirk Douglas tells his son Michael, ''I'm more proud of how you have handled your success than I am of your success.''

''Hollywood Dynasties'' tries to find a middle ground between the academic books on ''cinema'' and the gossipy books on ''the movies,'' and in this it succeeds.