Chill out, OP. At 12 I was caring for other people's kids.
Foul language? Everyone has different rules. You can correct "your" kids for using it, but not the others.
Rough play? Why are you stepping in? Teach your charges that it's okay to politely say that they don't want to play rough like that. If the older kids still don't stop, then you can step in. "Larla asked you to stop playing rough. Please respect her and stop." Or move your kids to another part of the playground.
Breaking the rules by running up the slide?

I cannot believe you're getting in a tizzy about that. That's hilarious. When was the last time you were at a playground?
You need to relax. Focus on the kids in your care.