Ahoy, Heidi!
How exciting that you are planning to embark on your very first Disney Cruise Line vacation! DCL makes the check-in process so easy, it is equally as easy to depart from Port Canaveral or Miami. You should choose the cruise that fits your family the best.
On our first cruise, we had three days at sea, and we STILL couldn't do everything that there is to do on the ship! I know it is sometimes confusing choosing which itinerary is best for your family. Just know that you will have a wonderful time, regardless of where the ship stops. Also, you don't necessarily have to leave the ship while it is docked in a port. I usually book the best dates for our family, we have sailed 3 & 4 Night cruises to the Bahamas, 7-Nights to the Western and Eastern Caribbean. If you ask me to choose my favorite, it is really hard!
I will say that I definitely recommend booking the longest cruise that you can. The shorter cruises pass by SO FAST. Some more of my best first time cruise tips can be found
here.
I hope this helps with your cruise planning for your first cruise! Please come back and visit the Disney Parks Moms Panel as more questions arise.
Happy Cruising, Tracy V.