I agree. I like parents to sit with their kids, not with each other, and definately not standing in the back of the room. I cannot believe how rude they can be.
I have more experience with adult shows, where kids are present, and I have trouble with the parents assuming I am doing a kids show and they will go to the back to talk. So, there, they have to sit with their kids, because it is a show for the adults, first, and for the kids.
One thing to remember, is you can sometimes do an effect for one or two kids, and have it go over well, but bomb when there are five or more. I have had success with cards with kids as young as eight, it I do it one on one. But you do cards with a group of kids that young and there is no way.
It is much harder to do magic for kids, then some people immagine.