Dave- I wondered that too. That's why I suggested going to the hotel and meet the other family first and then go to the ship after breakfast. If its REALLY early, they may not accept your luggage and then you'd be stuck waiting for them to take the luggage while the rest of the group is eating breakfast.
The extra cab ride is probably going to run you $15 to $20 (there is a port entrance fee which makes that number jump up.) But it might be better than waiting without food the whole time. Again, how early is early?
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