Forgive me for being so abrupt, but if he only takes the time to see you once or twice a year, his reaction isn't worth worrying about.
If his reaction is negative, don't give him the satisfaction of knowing that it bothers you. You're going to do what you have to do, regardless of him; If he's behind you, fantastic, but if he's not, be the better person... accept it with maturity and move ahead with your head held high.
I spent way too much time at the beginning of transition worrying about family's responses.... some are intellectually incapable of understanding your condition