Age Restricitons at Play Areas

In the past month I have taken my children to two parties at local McDonald's with play areas. One was a newly remodeled location on a weeknight at dinner time and the other was an established one at dinner time on a Sunday. At both places there is an area for 3-12 year olds and another for 3 and under. I have two children who fit into both categories. Both times I saw children who were much closer to 12 than 3 in the area for smaller children, but what made it worse was they were playing tag and roughhousing where small kids were playing. While it bothered me that children who should be able to read the posted signs were ignoring them it bothered me even more that the parents were watching them (or not) and didn't make any effort to have them leave that area. At the new play land I let each of my children see the younger area before it go busy and then after that I told them they were not allowed back in because they were too old. I had to later hold my one year old for the rest of the party except when he was in a high chair because it was way too crowded for him to play. Tonight he was almost stepped on by a kid who was about as tall as me and easily outweighed me. He may very well be twelve, I'm not exactly tall, but he was playing in an unsafe manner and his dad just kept reading the paper. I hope that I manage to be a more observant parent as my children get older and need less constant supervision because if your child is putting other children in danger it is your responsibility to do something about it.