Some of you guys are sounding like a defeatist attitude. The world is what you make it. So don't even try to teach the kids anything, or be neighborly because of what they might do? I think this is a poor show my friends. No wonder you feel sad about it, because you know you had a chance to do something real and dropped the ball by not even trying. No offense, but hey.
If you were a nighbor of mine and let them play with a rifle without getting permission from me or the wife, the best option for you is that we would have words at about 90 decibels.
Most likely I would call the police on you.