Everybody is different, and you'll have the best idea of the reaction that the person/people you feel like you need to tell will have.

For me...telling my family that I'm bisexual came after years of trying to hide it, and weeks of feeling like I needed to let them know. My family is very religious Mormon, and I wasn't sure how they'd react--though, I didn't expect yelling, crying or disownment or anything of the sort. And in truth, my parents and sister were all very supportive. (I don't think that it's any of my extended families business, at least until the point where I bring an hypothetical girlfriend to a family party)

Coming clean to my family has had an added bonus--my mom no longer hounds me about getting married and having kids. If I had know she would react that way, I would have told her YEARS ago!

Whatever you decide, I wish you luck. It's really hard, and I have no way of knowing if it'll be worth it to you.