Here is a list of links to
DCL resources
DCL Official Site
Dave's DCL Tribute (be sure check out the "External Links" section for more resources

ie Cast A Way Club

)
Magical Disney Cruise Guide (see links on the left)
The Magical
Disney Cruise Guide is the free version of the passporter (therefore it might not have everything the passporter has - but it is very complete!)
The DclTribute site has a list of "noisy" rooms so you might want to avoid those listed in order to get "the best cat 9 room".
Since it's your first cruise I would try to be at the terminal by 11am. Gives you time to check in, register your kids (if any) with the kids clubs, look at the map of the Bahamas on the floor, check out the model of the ship and see the real ship docked outside. There are also comfy couches and tv's that are showing Mickey cartoons.
Boarding usually starts around noon.
Everyone is supposed to be off of the ship by 9am. I would not book a flight out of MCO before noon.
Booking question: If you book through DU you can use your Disney Visa to get a room credit and you possibly would get a better rate than through
AAA. You should get quotes from both. Make sure you're comparing apples to apples - have them include taxes and fees and any room credits that you can get from the visa/first time cruiser/
travel agency rebates, etc. That way you can make an informed decission.