A few things:
I really wouldn't dwell on the thought of future children and all that right now.
Yes, you being poly does not make you suitable for a lot of people. And that is okay. There is nothing wrong with not being suitable for everyone you want to be suitable for. Do you really wanna date them all? You're one person. This need to be desired by whomever... it's not good. It's not good at all.
Society has told us all that the right way to love (romantically) is from one person to another. Clearly enough human beings have realized and recognized that despite what society has conditioned us to believe, we still feel the way we feel. We still love more than one. We still desire intimacy with more than one. Yes, we're made to feel bad about it.
But is this YOUR life to live, or someone else's?