Having a well-liked alien race handle the subject is the best way to go about it, agreed. If they can do that, then we can refine from there and make a major CHARACTER homo/bi.
I'm leaning twords bi myself simply because it can be handled with humor, like how I handle my "bi-ness" in real life.
CAPTAIN: "So, bringing Commander Swarth to the dance, Number One?
XO: "Naah, we broke up. Stupid women, they're all the same."
CAPTAIN: "So you're not going after all?
XO: "Depends if Lt. Hoark makes up his mind or not.
CAPTAIN: (deadpan) "Oh that would be nice you two make such a cute couple."
...see? Not so hard, and it's silly.