Achilless, I'm surprised at some of the responses you've gotten, and a bit disappointed.
The choice should really be Joshua's, whether he wants to wear a tux, a kilt, or a wedding dress. Wedding dresses can look so good on one person, and horrible on another, depending on body shapes, and should be tried on to make sure. I prefer a simple dress without a train, and trim, simple sleeves.
A wedding is such a special day. No matter what you or he wear, you should both feel you look just as special as the day, or just throw on a pair of cargo shorts and a t-shirt, say "I do," and jump each other's bones. Whatever you choose, let it come from within, and let it reflect who you are.
Best of luck to you.