Help: questions on playground etiquette.

Yesterday we took my son to the playground in a nearby mall. It was weekend and there are many children. My son was obviously the youngest. Many kids are way above the 42-inches height maximum but the parents still let them play there. These big kids run around wild and don't pay attention to little toddlers that are slow and clumsy.

So here is my first question: should we tell the parents with big kids to leave the playground? Esp. because they could easily trample over the young ones?

There was a big kid who was a bully. We saw him pushing other kids and even made one cry. Then he saw my son toddling around and pushed him hard on the back. My hu*****and saw his intention and shouted "no" to try to stop him. But it was too late. My son fell and started to cry, and the mother of that kid gave my hu*****and a dirty look for him shouting at the kid.

And my second question is: how should we as parents handle such bully behavior from other kids? What should we say to the parents?

Thanks for any advice you have.