Another 2 cents: You are their father. What example are you setting by waiting, waiting, for a moment that is "right" in some way, to tell them? And what example would you be setting by telling them soon after you know you have a gay side, and are comfortable with it?
That said, nothing should happen until you are comfortable doing it. I'm just all in favor of moving THROUGH discomfort instead of sitting still in it. Good luck!