Originally Posted by Blackcat31:
This is exactly what I do.
Frankly considering the massive liability a running child could potentially bring to the provider Im surprised that being firm and direct isn't the obvious answer for everyone.
I'm thinking being sued in court for injuries that happened on your property due to a parent not listening to you would suck majorly so wouldn't finding the strength to be firm and addressing the parent point blank would be much easier.....and cheaper ? 
Thank you everyone for your responses.
Blackcat, yes you are right, being firm and direct SHOULD be the obvious answer, but I'm very reserved and shy by nature and I don't like to correct parents. I feel like I shouldn't have to tell the parents to keep an eye on THEIR kid. But, yes, in this situation, I do need to grow a pair and take control...