I told my mother in early March. Initially, she shocked me by being 110% supportive. She said she knew this was an issue for me ever since I was little, and that I ought to do whatever I needed to to be happy. She said to ignore what other people thought, that they didn't matter. Since then, though, she's been trying to undermine and call my transition into question - by things like telling me what a 'handsome man' I am, that I could have been a model, etc. - this after I told her that being called handsome has always hurt my feelings.
My sense is that this is the kind of news that - for all but the most socially enlightened people - really has to be given time to percolate and settle in. People are going to have strong feelings about it, and to some extent we need to just let them have those feelings. I might have to distance myself from family a little until my transition is complete, just to protect myself. I am a longtime member of Alanon and have found upping my meetings very helpful!