All the men in the wedding party should be wearing a tuxedo if you will be. Being the only one in a tux will make you look oddly overdressed. Indeed, if your wedding is going to be formal then all the men in attendance should be wearing one as well. This rarely happens because so few men actually own one, or will bother to rent one but still, it is proper. By the by, there is nothing wrong with an evening wedding with the men wearing suits. It's simply a matter of formality. If you want a formal event then tuxedos are correct. If you do not, then suits are fine. Also, don't take relationship advice on SF (or anywhere else on the internet, I would say). They know nothing about you or your wife to be.