Admittedly, we did not dress up on formal night. Looking back on it, we kind of wish we had. It would have been nice to have a picture of the family with us all dressed up.
That said, people were all across the board in what they chose to wear. Most women were in dresses (cocktail type) and most men were in sportcoats and jackets, mostly with ties. We did see a few folks in their tuxedos and more evening gown-styles. Mickey and Minnie both get quite dressed up, so it's fun to think about taking a formal picture with them if you have the opportunity!