I think it's natural to come out to a friend before family, and I've ended up doing it myself. A family subtly pressures you with expectations, even if they don't mean to, especially from the parents. Although you form a bond with your friends, you don't get the same kind of pressure as you do from your family. It makes coming out very hard...the only reason I managed to come out to my parents is because they found out that I had clothes that weren't men's clothes. (Protip: Try to get it on more intentional terms. Goes over much better. I also told my dad, who seemed like he could take it much easier, and he helped calm my mom down because she was the one who found the clothes suddenly.)
I don't know how well you pass as birth-male, but my friends weren't surprised at all when I came out to them, and I think it will probably be the same for you, especially for a friend you feel so close with. That, I think, will make it easier.
As for reactions, I'm sorry to say this, but there's just no good measurement. Some people will take it very well, some people won't. There's two strong factors that work with your parents, though: The love of a mother and father is very persistant, and they will still care about you even if they hate transexualism. (My mom took it especially hard) However, on the flip side, it's really hard to accept that your child ended up transexual. It can be eased up by letting them know that it's not something that they screwed up in raising you with.
Remember to give anyone you tell time, try to be clear, and don't opress your transexualism or their cisgender nature.