I have 2 daughters and as painful as it was, I came out to them the night before my partner and I flew to Canada to get married. My oldest was 16 and youngest was 13. The oldest said she had as much figured it out, but the youngest was the toughest nut to crack. She didn't understand and I spent a lot of time with her talking and listening to how she felt. Now, she is one of my biggest supporters. The oldest is, too. The oldest writes pro gay marriage papers in her English class at college. The youngest one outs herself to her bf's and tells them if they have a problem with her moms, they need to move on. I am a very proud mom of two beautiful girls, but it wasn't easy coming out to them.
You need to be honest with them and tell them, listen to them and show them that your being gay in no way diminishes your love for them. Allow them to soak up the revelation and process it how they will, and be there the whole time loving them through it. Remember as tough as it was for you to come out, it will be that tough for them to reconcile themselves with it. Seek family counseling as well, someone who is gay friendly who can help them through it.
If everyone cared and nobody cried, if everyone loved and nobody lied, if everyone shared and swallowed their pride, we'd see the day when nobody died. IF EVERYONE CARED/Nickelback