The return flight home at 12:50 p.m. should work fine for your family.
Disney Cruise Line recommends that
flights be made after 11:25 a.m. which is approximately four hours after the ship arrives Port Canaveral.
My recent experience with
disembarkation day also shows that an early afternoon flight should work well. Once you debark, you'll get your luggage and go through Customs. This process is very quick and extremely organized.
The in transit time between the port and the Orlando International Airport is approximately 45 minutes. You will need to wait for the bus to complete boarding and traffic delays can occur.
In the DCL "Welcome Home" sheet that will be left in your stateroom on your last evening, DCL requires that guests with flights prior to 1 p.m. disembark by 8:00 a.m. If you do not disembark by this time, DCL will pull your luggage and require your family to check in at the Airport. I would exit the ship on time so that you can utilize the
Onboard Airline Check In service.
Enjoy your first cruise. It's a magical way to travel!