I am not a part of any playgroups but we spend a lot of time at parks. I am the mum that is playing just as much as my DD's so I am always very involved. I have no problem telling other kids if I think they need to think about what they are doing if it is affecting my DD's. DD1 is a very gentle polite girl and if someone takes something off her then she tends to just move on and if I see she is not upset about it then I just let her go though. DD1 has been pushed off a slide by 2 older kids running up it and pushing her out of the way, she actually fell over the side. Scary as all hell for me. Lucky she was okay but it that instance I actually yelled at the other kids, they were old enough to know better. There parents just sat there and watched, did not react in anyway.

I think there needs to be a bit of free play but parents also need to watch and be responsible for their kids actions and be there to pull them up when needed. Regards to at your home. I agree, your house, your rules, after all you have to stay there after everyone goes home.