It's not my decision about your nephews and nieces, obviously. I have a niece who defines herself as a lesbian and I see her at holidays with my son and her girlfriend both there. We politely don't bring the subject up, I inform my kid thoroughly what I believe and instruct him he is to be NICE to EVERYONE!
I can't speak for your family. Honor their wishes is my suggestion, and I assume you do that.
I believe you know what I mean about the children. As soon as gays get marriage licenses they will rush to adopt children. THAT is the biggest issue for me.
Name me some the "special rights", other than adopting children or become foster parents, that you want but can't get. Please. I can't think of any---at least that are a benefit. With every benefit of marriage there is an equal liability that tags along. Marriage has more to do with families---environments for raising future generations--than it does with sex, or even "being in love", at least as far as the State's interest is concerned.