Age is a tricky thing, I have one very good friend especially who is 15 years younger, but when we do catch up it's only certain places (gym, eat out, cinema, walk etc) and would be very weird to go on a night out with their friends. It's also more like a brother relationship I guess. Similarly I've been a mature student at uni and you do have to hang out with young people, or you're isolated. But again that was usually working on projects or study related.
Gary's other issue is hanging around kids playgrounds on his own with that stuffed mickey. All it will take is some Karen to panic and he could have a whole situation on his hands