Ideally, it would make sense to me that, ok, as a gay couple be married, but - and this is especially if your child is the opposite gender you are - make sure there is someone - an aunt/uncle(depending on the gender of the child), a close friend of one or both parents that is the opposite gender of the child, someone like that - that the child knows and trusts from a young age so that if he/she ever needs advice/help/whatever from an adult of the opposite gender who cares for them, they have one(at least one). To me, that makes the most sense.
this is usually what happens. and what happens with single parents as well.
and some kids don't get along with their same-gender parent (like, say, Bono or Bruce Springsteen) and seek out this male-male or female-female solidarity with other family members, close family friends, etc. i think it's silly that we think that our parents are the start and finish of our family. it precisely does take a village.
i never talked about sex with my parents, but that doesn't mean i didn't have adults with whom i could talk about that kind of stuff with. i never felt any solidarity with my father on the basis of gender -- perhaps that's because neither of us were keen to ogle the Dallas Cowgirls or whatever it is that some men do to bond with their sons -- and i really can't tell you where gender came into play in my upbringing. yes, my mother is who she is because she's a woman, and the same with my father as a man, but in actual parenting, i don't see how their opposite sexes created some sort of alchemy.
i also think that the yearning for the absent mother or father is probably more of a condition of single parenthood, where one parent has left and that's the absence that has felt. if a child has two parents, i'm not so sure that there's the same sort of need. and, again, this is where families and friends tend to come into play.
and from what i've observed, gay parents tend to form very, very strong networks and bonds with other gay families. there's a strong amount of solidarity there, and no absence of same-gender role models instantly available to you.
and, ultimately, no family is perfect. perhaps one has a loving father, but he's working most of the time. should he not get married because he's not there to make his magical alchemy with mom?
the points, here, are twofold:
1. having children is not a prerequisite for getting married
2. there are many different forms of successful families, and many successful families are non-traditional, and many traditional families are abject failures; thus, the success of a family is not contingent upon it's form, but upon it's content