I have a suggestion; establish some basic guidelines for what is and is not acceptable behavior before you go out with people you do not know.
At Kid's ropeups in the past, my youngest daughter was subjected to a kid swinging a knife in her direction. Both of my daughters thought he was really trying to cut her. The father did nothing. Period. She was afraid to go play with the group for the rest of the weekend and was sad because of it.
The next year, two kids stole my daughters lunches. I pointed it out to the father (different father) and he did nothing. Period.
My daughters had no lunch that day.
Later that same day, one of these little theives threw a stick at the other little theif and hit my youngest daughter 1/4 inch below her eye. It took 4 stitches and an emergency visit ($483) plus her eye was purple and swollen for a few days.
Free-for-alls are great fun until it is your scared, lonely, hungry, kid hanging dejected in camp or in the emergency room.
My daughters have very little interest in the Kids ropeup anymore. They immediately point out the instances I just listed.
It angers me that parents are so un-caring about my children that they are willing to knowingly let their kids cause my kids to suffer. They take great care with a belay but are willing to let knives swing, lunches disappear, and violence to go unchecked.
Assholes.