if your plane lands at 8:50 and we assume its not late, giving an hour or so to get off the plane collect your luggage and get to the taxi line, (which would be speedy time considering Miami) that puts you in a cab about 10AM. Another 15 to 20 mins to get to the port and you are at 10:30 ish. You can probably get someone to take your bags by 11AM. You can probably start boarding by 12 or 12:30. I'm not sure you would be saving yourself a whole lot of waiting time if you try to throw a breakfast in there. In fact I would say that if you do, you are ALL going to be waiting in line because most people start arriving by noon.
You might just want to skip the breakfast and meet on the ship. have a buffet lunch then.
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, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013