Kids like instant feedback. Reactive targets are key. Check to make sure what is allowed on your range, of course, but clay pidgeons, overripe cucumbers, wormy apples are all great with .22's ...... water jugs are a "hit" with centerfires! Spinning metal target or "dueling posts" are fun, too. Bowling pins, empty shotgun shells..... if you are made of money, full sodas....
I have seen guys hot glue aspirins on black sheet of construction paper for kids to shoot with bb/pellet guns.... the thing is the kids need that instant feedback.
TheGolden Rule of Tool Use: "If you don't know what you are doing, DON'T."