More then likely, having experience with alot of labs he'll get pretty big. Chocolates are supposed to be the largest of lab breeds. I'm sure the other dogs will know when to stop, especially it being a puppy, dogs kinda "know" Plus your friend could tell them to cut it out if they get to hard on the pup.

A way to kind of check how large it's going to be is by the paws. Large paws= large dog small paws= small dog. But then again that's not always acurrate.