I wear a Spanx top -- the shape of a tank top. It comes down to below the waist. I like it because it smooths out the muffin top and sort of fattens the belly. It also sort of flattens the "girls" which I don't appreciate, but the pluses outnumber the minuses. Getting the dern thing on is a battle, though. I suppose if the size you choose goes on too easy, it won't do the job you're looking for.
Have fun at the wedding! Dance up a storm!