Try the soft/teaching approach, then video/photography and prosecution. If you are really ambitious, most public libraries archive local yearbooks (or used to) ... so it's not impossible to identify the kids (for the police, not acts of personal vengence).
Please try to refrain from becoming a police blotter entry:
Street justice, extraordinary overkill edition: A boy throwing rocks at cars took a crossbow bolt to the belly yesterday, apparently as retribution for throwing a rock at a Toyota RAV4. The RAV4 had several passengers, one of whom literally went medieval on him, pulling out a crossbow and shooting the kid right then and there. Funny, I would have taken Goliath for more of a Chevrolet kind of guy.
The injured child is being treated for "injuries that were not considered life threatening" at a Children's Hospital in San Diego. Moral of the story:
Do not throw rocks at cars are large enough to carry medieval artilleries. I mean, you shouldn't throw rocks at any cars, but especially not the big ones, y'know?