Good info and one other thing to consider
"We were just at Castaway Cay Tuesday January 14,2014 and yes they do still do the 5K
To avoid the rush, when u get onboard, go to the Port Adventure desk and reserve your spot. It's free. They give u ur bib then and at the end of the 5K u get ur "medal".
It was lots of fun. Enjoy."
Nice to know that you can sign up right as you get onboard! We did it last May 2013. We are set to go again this year in May 2015 after running the Expedition Everest Challenge.
Another thing to consider; we quickly dropped our non-valuables, ie towels, sunscreen etc on beach lounges as the leader walked us by them so that when we were done running we had enough seats together in the area we chose.