He knows how I view gay marriage....and I am sure that he knows that I am not there to show any support for a gay marriage movement - he knows I will be there because he is my cousin. This reason is enough.
.My wife says that a Marriage should be between a man and woman --- and we pretty much agree that there is a place for civil unions. We're going together
I think you are doing the right thing.
What amazes me is how quickly most here jump to a decision. I think I'd want to take a few days to think, ponder, possibly pray. I'm initially conflicted, not sure what I'd do. We are taught to "love the sinner, not the sin"....which would seem to suggest that you should go. OTOH, marriage is a sacrement..though not "specifically" when not done in the Church..so does going in some way condone the sin?
Another question to ask yourself: If it wasn't for the fact that this was my cousin and very close and dear lifetime friend, would you go? Probably not, I'd surmise from your comments. Therefore, does going in this case make you somewhat hypocritical? Possibly so, but it's only important how you feel about it, and yourself, in this one instance. IOW, if it was a distant relative, or a business associate, I gather you wouldn't attend.
I think, all in all, that you've made a decision that you're comfortable with, moreso since your wife agrees with you, and that you should just go, and go along..