DCL 'officially' recommends not booking flights before 12:30pm but they do allow Onboard check in for any flight 11:30 am or later. Our flight was at 11:40 and still had plenty of time to eat before boarding.
If your airline participates with onboard check in and you're using DCL transportation back to MCO, Onboard Check in is available & free. Your boarding passes and luggage tags are delivered to your stateroom the day before you leave. You then place your tagged luggage outside your door by 10 pm and don't see it until you arrive at your home airport the next day so no need to wait in line at MCO to check bags. Simply hop off the bus with carryon bags and head straight to gate.
To use OBCI, you have to be off the ship by 8 am at very latest. Bus departs by 8:10 and you'll be at MCO by 9.