I totally agree with some of the above advice. We just got back from our cruise and have seen what can happen. We decided to go the day before to relax some. One week before our cruise we got an email saying that our 2 hour stop over with Air Tran had been changed to a 4 hour stop over. After waiting in Atlanta for 4 hours we found out our flight had been delayed a further 1.5 hours! Thank goodness we left the day before otherwise we would have missed our ship.
Another thing, I agree with staying away from Expedia!
Have a blast!