You could also put in for room service breakfast and just have them deliver it late. You will still have to wake up and trow a robe on for the server but you wouldn't have to be up early enough to shower/dress to get up tot he buffet or dinning room.
I'm a night owl too but when I cruise I still wake up early enough to get to the dinning room for breakfast. Also, if you are in port, you are going to be getting up early to go into port.. a little earlier and you can get breakfast first too.
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