If you want to do it, run it however you want to. It's your game, your players, your world...you know it and them better than we do.
I would just caution you to NOT do anything that can't be undone, though, if things don't work out as you wish. Whatever you do, it needs to be able to be swept under the rug or (ha ha) put back in the closet, if need be.
My own experiences (in the game, of course!!)...
Firstly, you must understand that I love world-building and create things that are never seen by the PCs just for the love of doing so...
I have some cultures in my world were homosexuality isn't tolerated (it's NOT homophobia...I find that term ridiculous...why would anyone FEAR a homosexual?). The reasons are different for different cultures. In some, it is a religious bias...in others it is a survival thing (sexual relationships not capable of producing children aren't useful to them)...in others, it's just disgust, pure and simple.
In other cultures it is tolerated, though not encouraged. The reasons are, again, varied. Religion usually plays a key role, though. It is usually not discussed and not flaunted.
In other cultures, it is seen as an individual choice. Experimentation is ok as long as no one gets hurt. The choice of the individual overrides the judgements of the society.
In only a couple of cultures is it actually ENcouraged. These are, quite naturally, cultures that are not overly large or widespread (how can a culture spread when its people can't, or won't, reproduce?). The only human one that stands out is an Amazonian-type culture that is an elite sub-culture rather than anything widespread. They breed only for duty and couple with their own sex for pleasure.
Overall, though, sexual orientation plays absolutely no role in my campaign. There have been overtones when the PCs were on leave from their wars and sought out prostitutes or when a femme fatale attempted seduction or when an NPC traveling with them got them into trouble for getting caught with a nobleman's daughter, but these are all either minor "color" for the campaign or are plot devices like any other adventure hook.
In the end, it's your campaign and only you can decide what is best.