I say if you bring your child/children to any type of gym they should be of age, and if they are going to use the equipment they should do so in a proper manner. Nitwit said that one of the kids were belly down on the treadmill. Is that using the equipment properly? I don't think so, and that would grate my nerves to see that. If they are of age and acting in that manner then they need to leave.
There was this one lady that would bring her kids to Pro-Fitness and they would sit on the floor behind the treadmill she was using. They would try to touch the belt as she was running. How safe is that? I do know of a couple of people who complained after she did this for a few days in a row. I haven't seen her back since.