If i had to guess i would say that 90% of your fellow passengers get dressed up and take part in all that formal night has to offer. The food and presentation is exquisite, you get a chance to have a formal family portrait taken, the whole evening has a feeling of a really grand party. You don't need to go out and buy a fancy formal gown. If you have a dressy cocktail dress, a long dark skirt with a dressy or sparkly top. Think of clothes that you would wear to an evening wedding. As for the teens - boys will be fine in dress dockers type pants, dress shoes a cotton shirt & tie. Girls - a nice party dress or skirt & blouse would be fine - dress church clothes. Husband - dark suit, dress shirt + tie or suit separates. Your kids might surprise you and want to get dressed-up. My son was like "wow" i look really good all dressed up!