#1. I'm an upfront kind of gal...I'm straight up and honest, but polite at the same time. There is a fine line there LOL
I would say to her, " Dude why so rough man?" and we would probably leave.
#2 I would tell her "Hey your kid John just hit Lily" if she didn't do anything about it, I would go and talk to Johnny, hey I see you're hitting are you mad about something? If he's just being bad for the sake of being bad I would ask him to go for a time out, or tell the other kids hey how about we all go over HERE away from Johnny and play until Johnny can be nice?