My best advice is to work with a reputable travel agent, preferably one who is a cruise specialist and one who has actually done a Disney cruise. Their assistance can be invaluable and they will be able to help with all the arrangements and answer all your questions so you won't have to hassle with all the details. Plus, their pricing is going to be exactly the same as Disney charges, so it makes sense to utilize their services and expertise for free. Besides, if you book with the cruise line and have any problems, who do you think they represent?
With that said, I always recommend getting a flight after noon just to be on the safe side. Anything sooner does not allow for any delays. Plus, you want to be at the airport and least 90 minutes prior to the flight - again, just to be on the safe side.
There are plenty of really good and affordable transfer companies from Orlando to Port Canaveral. Your agent will be able to help you with this as well as assist you with the type and location of cabins.