Welcome aboard, Jeff!
Disney Cruise Line offers so many amazing activities not only on the ship but in its ports of call, and in your case, even in Miami upon returning!
I highly recommend the
Hop-On Hop-Off Miami City Tour with Airport Transfer adventure. Disney has you covered with transportation to some of Miami's most popular spots, luggage storage while you explore, and then transfers to either the Miami or Ft. Lauderdale airports. It doesn't get easier than that! Your boys will love the double decker bus that you ride on one of three loops: the Miami Beach Loop, the Uptown Loop, or the City Loop. Check out what seems most fun to your family and choose that loop. Then, ride along until you get to a spot you'd like to explore. Hop off, and enjoy the day at your pace. Just jump back on when another bus comes along, every fifteen to thirty minutes. You're also free to stay on for the entire loop which takes from 60-90 minutes, depending on which loop you've chosen. You'll get to see it all, then loop back around to what seemed fun and hop off there for some exploring.
When it's time to go, just take the bus to the luggage storage area and you'll board a transfer to Ft. Lauderdale Airport. The transfers run from noon to 2:00 to Ft. Lauderdale, so you'll have quite a morning of fun to keep you busy until it's time to go, and best of all, you explore where, when and for as long as you'd like! With three little ones, that makes it super convenient!
The other option I'd suggest if you want to store luggage and explore the city is to rent a car from the port and return it at the airport, but honestly, it's so much easier to let Disney do the planning and this adventure is the perfect way to end your vacation!
Have fun planning, Jeff!
Marcy