Welcome Back, Lorelei!
Just last week, I was onboard the Disney Dream for the Castaway Challenge, as part of the Disney Princess Half Marathon weekend, and it was amazing!
Each time one of the Disney Cruise Line ships visits
Castaway Cay, they have a free Castaway Cay 5K run. To sign up for this, you will need to visit the Guest Services desk by the day before your stop at Castaway Cay. At this time, the minimum age to participate in the 5K run is 10 years old, so I am sorry to say that your little ones will not be able to run with you. You will be able to check them into Scuttle's Cove on Castaway Cay prior to running (or walking) the 5K.
One of the coolest parts of the free event is the new medal for 2015! It is an official runDisney medal, and I was so happy to have earned it. Another perk of running this race is that your group is the first to exit the ship at Castaway Cay that morning.
I hope this answers your question, Lorelei! Keep coming back to the Disney Parks Moms Panel with your questions.
Happy Cruising, Tracy V. (just keep cruising, just keep cruising...)