I would support them, and anyone in my family that had a problem with it could go eff themselves.
It's sad so many people are disowned and abandoned by families for something they can't help. They are still your children and the same person you love, they just have a different preference when it comes to what they are attracted to.
Tell them it doesn't matter to me because I still love them and ask what they wanted as a side dish with dinner. My husband would probably say something like "well, now that you know too, can we go fishing?"
Love them just as much as I did the day they were born. My baby is my baby; gay, straight, transsexual...doesn't matter. I would never try to make my child suppress their feelings because of judgement from others or anything like that.