I think as long as you look nice. You could do pants and a flashy top, your hubby could do pants too and a tie. I was on the Brilliance last christmass 2005. I saw many people who didn't dress up formal.
Also many are correct, you can just dress up for dinner and change. We did that many times.
Think of it as a glamoerous night on the town with that special someone, so have fun. How many times will you guy's every dress up again.