I think you did the right thing in calling 911. At least the parents will be informed and, if they are at all concerned, can correct it. I personally don't have any kids, and wouldn't know what to do to correct the problem myself. From experience, just telling misbehaving children that they shouldn't do it doesn't work if they think they're playing games with you. Leave the disciplining to the parents of the kids - who hopefully will take care of it instead of just letting their kids do whatever they please.