Speaking AS a gay guy :P me and my father did most of the "classic" father/son stuff whilst I was younger..
IE. Playing football, various other sports, giving me advice on my first girlfriend.. etc.
Even though I've always known I was gay, I still had girlfriends (as do most gay guys) for 2 reasons, 1- to make sure, because when you're younger you always hate that you are, and 2- as a disguise so people didn't know.
What I would do (If I had a son who turned out to be gay) is do exactly what I know he wants from being in that position myself..
I wouldn't treat him any differently at all, gay guys are still guys, there's no reason they can't do "guy" stuff and have fun. I was lucky to have a wonderful dad, who, aside from growing up my whole childhood with a slightly homophobic attitude from him, when I came out to him, was loving, supportive and not afraid to joke around about it whilst still being supportive when I needed it.
and for the prospective fathers: if you are concerned about it, let him come to you everyone will tell you when they're ready, there's no need to make a big deal out of it, we don't come out to be made a fuss of, we come out as a way of reinforcing that people are okay with it. -> if you think the relationships are much different for gay guys, they're really not.. :P If you can give good relationship advice it will work for any relationship whether it be gay/straight ^_^