"Hollywood's Children" barely constitutes a once-over for its subject, child actors of movies then and now, but it is still fairly engrossing, as would be almost any show that gave one a chance to see Spanky McFarland as a grown man, his puffy cheeks now turned to bulldog jowls but his sense of mischief still apparent.

The one-hour film, at 8 on Channel 26, was obviously made with sale to commercial stations in mind--there are suspiciously regular fades to black--and does not conform to what ought to be public TV standards. But what the heck, it's darned enjoyable. Writer-director Gene Feldman goes back to the earliest silent movies, with their imperiled and abandoned tot heroes and heroines, and up to today's perverse new sexual objectification of children in movies and TV commercials.

When Chaplin chose little Jackie Coogan to appear with him in "The Kid," a new element was added to moviemaking; narrator Roddy McDowall (a child star himself) says this was the first time "an actual child" got a lead part. The Coogan of today, affably bulbous-nosed, talks about his youth on the screen and, near the end of the program, discusses a possible show-biz career with his grandson, who landed a part riding a moped on "CHiPs."

Diana Serra Cary, who was Baby Peggy in "Captain January" and other silent films, says she retired at the age of 10 and that by the time she was 15, "I had the feeling I was a senior citizen." She earned "$2 million I'm sure of and another million I'm not quite certain of," but until Coogan sued his mother and stepfather and California enacted The Coogan Law, kids could be gypped out of anything they made before the age of 21.

Young Jackie Cooper "always made them cry," says one old-timer, and a scene from the rarely seen "Lone Cowboy," in which Cooper plays a lad who learns his father has died, shows why. But Cooper himself is not interviewed, and there is none of the kind of bitter reminiscence about exploitation of child stars that Cooper recounted in his raucously irreverent autobiography, "Please Don't Shoot My Dog."

The old clips, assembled with the consultation of film historian David Shepard, are full of charm; scenes of present-day aspiring child actors are darkly charmless. A young model is photographed by a photographer who notes ever so warmly that children are "an effective force in the marketplace," and the girl herself recalls, "Oh, 'Facts of Life'--that was my first sitcom experience." The whole idea of childhood seems to have become as polluted as the skies over Gary, Indiana.

By contrast, three of the most captivating child-star performances from the '40s are briefly recalled: McDowall himself in John Ford's unforgettable "How Green Was My Valley," the late Natalie Wood in "Miracle on 34th Street," and Peggy Ann Garner in Elia Kazan's "A Tree Grows in Brooklyn." For the sublime gratification of getting to see the present-day Peggy Ann Garner all grown up and still full of presence, "Hollywood's Children" will have at least one aging viewer's everlasting gratitude.