My husband wore a dark sport coat to dinner most nights. The formal night he wore a dark suit. I think as long as you dress up for dinner, like going to a wedding you will be all right. Now that doesnt' mean there won't be the few people that won't dress. They will wear jeans, but let me tell you this, they will be looked at from the other pasengers with a critizing eye. Jeans are not appropriet wear in the dinning room.