Being a "veteran" cruiser i don't stress over this kind of stuff anymore. I bring one carry-n that has all the basic daily toiletry essentials and medications. The second carry-on is a backpack that i put the camera, walkman, book or magazine, bathing suit,/with t-shirt(cover-up) change of undies a clean shirt for dinner and a pair of pants if i wear shorts to board the ship.
When it comes to luggage handling - getting in the day before is a huge advantage. As long as your luggage is tagged properly - when you hand it over to the porters at the pier, it will get on the ship and it will get to your cabin.