The process is the same for all cruise lines. You arrive at the pier and your luggage is handed over to the porters, who will then load it into some transfer bins which are then loaded by forklift onto the ship. Your luggage will get on the ship. The porters actively pursue tips however, and I usually give them a couple bucks per bag. Being that you will arrive in a Carnival chartered bus, the tip episode may be avoided. Don't worry about your bags getting on the ship. It may take a few hours before the bags get delivered to your cabin, so it is vital that you put a change of clothes in your carry-on. I usually include my swimming attire too.