That's a great place to start! My daughter had a good grasp of LGBTQ issues, too, and I think this made it easier. In my case, I did not wait for the therapist since I knew my daughter well... We were supposed to discuss this on Monday a week from now, but I couldn't take hiding from her any longer. I read everything I could about the issue sand asked for advice here, and, well, relied on her huge reserves of awesome to get us through.
Maybe not the most prudent advice, but the only choice I could make given the circumstances. *hug*
Whatever you and his dad decide, you are ahead of the game with having a kid who understands the LGBTQ situation. Good luck and much love!
*hug*