I was told by a RCCL Rep when they were pulling out of Norfolk, VA and taking the Enchantment of the Seas to Baltimore they had deals with a few Hotels that you could leave your car at the Hotel for free if you stayed there the night before the cruise. Transportation to the ship would be provided. It would be worth staying at the Hotel and not have to pay $15 X 12 days to park at the Pier. I would call RCCL and get the names of the Hotels and go the day before.
Hope this helps !