I've been a wedding photographer for years and I can honestly say anything really goes. Wear what you'd like to wear. It can be casual to very formal. It's entirely up to you. The only thing that would be awkward is if you showed up wearing a nicer tux than the groom, or a wedding dress. >.> (Yes, I have seen that before.)
It's a nice suit, man! Wear it and enjoy the wedding and enjoy the free food and drinks.