If you make reservations the first day on the ship you shouldn't have problem getting a table. Be aware, children under a certain age are not allowed. I believe it's 13, but I'm not sure. I'll be getting on the Mariner when you're getting off.
Hey Freddie48, we were on the Mariner in 04, best cruise yet. Have never tried the specialty restaurants (except Johnny Rockets), but the food in dining room was great. Welcome to cruise chat. Have a great cruise. RB