Long ago, I learned a single sentence that sends obnoxious juniors away from me as fast as their little legs will carry them. Here it is:
Lean over to the child’s watcher and, as politely as you possibly can, just say, “According to the terms of my parole, I’m not really supposed to be this close to children”. Mom, Dad, or whoever they pawned off their hell-spawn onto will immediately grab the little devil and exit your presence!!