By the way I wanted add for Aerospace:
Excellent idea having a separate formal dining room - Carnival ships have two dining rooms, and many with two entrances on separate decks. It would be easy to set aside one deck as strictly formal.
Of course, it would make the Maitre D' a little uncomfortable to have to tell people they came to the wrong entrance, and someone would certainly blow his top and say he was treated rudely because a Maitre D' who discriminated against him for no reason when he asked him to go to a different area.
But you could fix that by just having the waiter escort the person to a different area of the dining room.