10% gay? Does that mean 1 in 10 times with a man you get aroused by a man or 1 in 10 sexual encounters is with a man?
I think you mean you are 100% bi. That is fine, by the way, but now I think you need to come to grips with yourself before you can tell your parents. I don't think, "Mom, Dad, I'm only 10% gay, don't worry," is going to fly.
By the way,take Allie up on her invitation. She's great fun to hang with.
Take care,