I can't believe someone makes MacDonald's ball pits "political" - ugh.
My own kids found a dirty diaper in MacDonald's ball pit one time. I nearly hurled. They were washing their hands for 5 minutes over that, and when I asked for a manager, I got a kid who looked all of 17. (They all look younger when we're older, LOL!) I don't really know how old he was, but he was YOUNG enough to just say thanks for telling him and go back to what he was doing.
We are talking about POOP in the balls, people.
This is the kind of stuff we put our kids in at places like MacDonalds, because the staff doesn't care about the ball pit. If that had been in MY town, I would have raised a stink over it, but we were traveling.
My kids didn't want to play in the balls anymore after that.
That doesn't really answer your question, but like you, I wouldn't want big kids in the balls with little kids. I think it's a bad mix.
Dawn