It's a public, communal decision. You already have to comply with the community's restrictions on whom you can select to marry. Sex is but one of those restrictions no different than marital status.
children? state dont give a damn about children in this matter
thats why they dont ask you if your going to have kids nor do they care
thats why people can get married with no intention of having them
thats why people who cant have kids can also get married
now if you want to start you own thread about how only people that raise kids should get married have at it, you'l probably come up short in that thread too but just like you invalid argument thats a different issue
By the way, your same argument could be used to further regulate or ban guns.
As I said, this is not a case of "it's harmful so ban it", nor is this a case of "it's harmless so legalize it".
A careful reader would notice that I haven't spoken out against gay marriage on this thread.