I am actually is the same boat, if you will. I will be flying in two weeks to see family I haven't seen in 3+ years. Grandmother is paying for me, my (soon to be ex) wife and daughters to come. She is paying for everything, because she knows we can't afford to come otherwise, and she's been planning this for a year as she knows she's gonna die soon (soon being relative, maybe years away). Some of my family on the other side "knows", but no one one my dad's side (the side of the reunion). We're flying up a few days before the actual reunion to talk to some of the family, and I'm going to come out to them officially then. At the reunion, I'm not going to hide myself, but I'm not going to flaunt it either. I'll probably be dressing andro, as I don't fully dress out. I just can't do it yet. If people ask, I'll tell them, but I'm not going to announce it or make a big deal out of it.
To be honest, I have a lot of respect for my grandmothers and some of my extended family, but my parents and brother, not so much.... because of other reasons, not trans-related.
Heh...maybe if I get a good enough pic at the reunion, I'll change my profile pic....