Kids or people without the dining package do not have to order off a different menu, in fact most children over the age of about 8 will not order off the kids menu.
The menus are not the same every night. They have a portion that doesn't change but most of the menu changes nightly. The menus are the same in both dining rooms.
Are you just trying to confuse people. 80% of dining slots are held for giving out on the ship. they are not that hard to get when you are on board unless you have a large party.