If your flight is scheduled to get in at 9:30Am, figure it will take 45mins to and hour to get your luggage and then another 30 minutes to get into a taxi and to the pier another 15 or so to get to the luggage drop off point... that puts you at standing in line at about 11:15 or so... Not enough time to bother trying to get extra shopping done before they board. There will be plenty of shopping time on your cruise. I'd just go and get in line then board as soon as they let you.. That gives you more "cruising time".
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