If everyone I dated were in a room, then I, a heterosexual male, very much might address that room as guys. As in, "hey guys, what are you doing here?"

I absolutely would not say "hey ladies"

It would feel too formal to say "hey everyone"

"Hey people" would be awkward

"Hey you all" eh

It might be better to leave it at "hey"

It might be best to just say "bye"