funny you should comment on the dress code. My wife and I don't have a dress code at work, the couple we went on the cruise ship do. We dressed up for dinner every night, me a dinner jacket or suit, and loved it. The other couple, while not in t-shirts, were glad to not have to where suits.
I think the dining rooms should police the dress a little better, suit and tie/ dressed up on one side of the dining room, casual on the other. This would solve the problem and still give people options.