Bring it up casually.. when people are just sitting around chatting.. it is not a big deal, so should be discussed as such
Maybe and i'm old and jaded - but any person who rejects you, solely on sexuality was never a good friend and is not the kind of person I would want in my life anyway.
It is 2017 Â - in most (not all) countries - a real friend may be shocked or surprised but is not going to reject you - even if there initial reaction is to freak out, a real friend will come back around and deal with it.. because they are your friend
When i was younger, my dad taught me a lesson - he told me that if you lend $20 to a friend and you never see them again (because they avoid you because they don't want to pay it back) then it is the best $20 you ever spent - because they were never a real friend. Same applies.
In most cases, my parents NOT included lol,i told my friends/family casually - If i made it a huge drama then that reflected more in their reaction