Kiddo
To be honest, I don't think any dad really wants to know too many details about his kid's sex life or wet dreams, you know? "Hey, Dad, I like guys" would work for me, 'cause then I'd know that if he brought home a guy for dinner it could be a date and I should probably be on my best behavior.
Apparently, one of my daughters from the future likes girls sometimes, and I just told her to make sure I don't hear any noises and to give me a heads up when a date's a date and when a friend's a friend. But I'd appreciate that as a dad with anyone. Just 'cause you're gay doesn't mean you can't have dude friends.
So, yeah, depending on him - at least in my experience - I'm sure he'll be glad for the heads up and still worry about you. It's a dad's job to want his kid to be happy. And if he gives you any static, well, you have to live your life.