Since they are accomidating you on getting onboard early, I'm sure they will be able to provide a place for you to keep your luggage safe during the wedding. I wouldn't worry about it. BUt when you get to the ship, mention it to whomever is guiding you onto the ship and they can probably find a place for it.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013