Marriage, yes.
I personally do not change my opinion of a person because of their sexual orientation. Honestly, I don't believe that there is a conscious decision that someone makes to become gay, and after a fairly long discussion with my uncle (who is gay), i've found that he never made the decision, he just realised that he wasn't interested in girls.
So just because of circumstance, why should somebody be disallowed a marriage, something which may (for them) symbolise their love for their partner?
Adoption, also yes.
Just because there is no female/male parent, there is no evidence that suggests that there will be anything wrong with the child.
Indeed, the only "funny" thing that happened to me while growing up around my uncle was that i learned to respect peoples' sexualities.