I think that you answered your own question, in your last paragraph. Tell those that you are comfortable with, and will support you emotionally. Do not tell those whose business it is none of, nor those that will create emotional stress for you. If, however, you and your "umfriends" (I like that) share mutual aquaintances, you may want to clear it with them first. Being teacher's and all, blah, blah,blah, you already know where I'm going with this.
Damn. Smart. Pretty. Redhead (sometimes). And now bi. I'm gonna come out there and kick Ratbastid's ass for getting to you first.

JK, but remind him for me what a lucky sumbitch he is...K?