Any time any waiter ever made any sort of hint about a tip, I always made sure that no tip was given, even when I was with a group. One time I even saw a bill with a rubber stamp on it in red "tip not included."

If you want to have some coins to give to the homeless, that is always a nice gesture. They do not take cards yet even if they all have mobile phones. So I suppose that some of them will have things like Apple Pay before long.