It was an unofficial wedding, really. I mean, they weren't like REALLY, really married.
How do we judge what counts as official when the characters exist across space, time, jand multiple universes? As far as I'm concerned they called one another husband and wife, good enough. It would just have been nice for some explanation of how River Song is now out of his time stream or something.
I still think it wasn't a real marriage to begin with. River married a robot Doctor.