Some more input for now, as I will be going to Port Canaveral in October for my cruise. I'm not sure about Carnival, but I'll be on RCI.
Anyway, Port Canaveral is about 45 minutes or so (mainly highway) from Orlando Airport. Not sure what Carnival's rate are for their shuttle to the port.
On RCI, staterooms are not ready until at least 1:00, so you're correct in that rooms may not be ready until 1:30.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas