There’s no better way to see the Disney island of Castaway Cay then to run a 5k first thing in the morning!
I saw this run mentioned on different Disney forums while I was researching before the cruise and was super excited for it. We registered soon after getting on the ship, but they also allow people to register on the day of. Just make sure you have an ID and your room key. I think kids are allowed to register also. I forget the age limit, but there were kids around 10 years old that were running twice as fast as I was!