Accepting family, but not enough courage to come out. Advice?

So I’m either bi or gay, but I’m not really sure. It seems like I’m only sexually attracted to males, but romantically attracted to both. My mom works with a lot of LGBT people, and tells a bunch of funny stories about them, so I know she’s accepting. My dad voices his beliefs a lot, and he’s repeatedly said that he doesn’t care if someone is gay or not. However, at times he can be very opinionated, and I’m worried that his stance on LGBT people will change if his son falls into one of those categories. I’ve also heard him say that he doesn’t think people can actually be bisexual, but that was over two years ago and his opinions probably have changed. My sister has talked mostly positively about LGBT people in the past, but has said some negative things about them too (such as she would never want to date a bisexual person). She is also in the more popular crowd, so I’m worried that if I come out to her, she won’t want me to come out to my friends because word might get around and it might hurt her popularity (people are a lot less accepting in that crowd). Anyways, I was thinking about coming out to my mom first, but then just never do it when the opportunity arises. Advice? (Sorry for the rambling) (And I want to come out to family first, then friends)