Well, thats a tough situation given that there was not really a lot that could have been done. However, if I were in that position, even if I was told not to leave my position, I would have to correct the situation.
At my old place, I was a breaker. Breakers had a section of the haunt to monitor and we reported things that were broken down or if there was a trouble group, we followed them and instructed the actors to keep their distance or be wary of their actions before anything escalated.
I have run into similar situations at my old haunt many times. Each situation would have to be dealt with specifically. Being that this situation dealt with kids, I would either remove them, or freak them out by poking them in full view of everyone or something. Showing them I can break the rules and will do so if I need to. Its helped quite a bit. Being that they are aware they shouldn't touch us, and we cant touch them gives some people some real crass and a willingness to do what they feel like. The best system I have heard of so far is a haunt with ear pieces. The ear pieces and cords were concealed of course, and if/when a customer was becoming unruly, they would say a pass phrase or so into their mic while pushing a button on their radio. This alerted security and called them in through a sneak door with a normal response time of about twenty seconds.
"If I ever hear , "Boo", "Hiss", or "Roar", I will personally kick you in the pants."