This will be our first DC& 7 day trip. we took the 4 day two years ago. How formal is formal night? Do the majority of men where suits or tuxedos? Do the majority of the women where full length gowns, or cocktail dresses?

Anything goes. Because it is a family-geared cruise, you'll see a mix of clothing. Some women just wear regular dresses, some wear fancy pant suits and some go all out in full-length gowns or cocktail dresses. Soem men where just sportcoats and some wear tuxedos. I love getting all dressed up because I seldom get to do so on land. :)