If you haven't considered it, you could always go with a first initial/unisex middle ground, although those tend to only work if your name is close to your given one. In the same vibe, you could just not show your sex until you feel it's alright to change it to male. As for who to tell individually, you could just tell who asks. In my about me, I have "ftm transsexual (IM/inbox me or wikipedia it for details)", which seems to work. No one's ever been unnaccepting, just curious.
I went from a unisex name to my actual one, but I guess the difference would be I never had my sex show. If it doesn't bother you, you could just allow people to keep you listed as female cousin, niece, sister, daughter, and the like until they want to change it.
Much luck, however you go about it.