Hi, Paul!
I have not done the 5K yet- I plan to on our cruise this July!
But I have been researching this topic as well so that I know what I'm getting into!
My understanding is that anyone 12 years old or older can do the 5K. It is not a "high pressure, serious" race. It can be walked, run, or a combination of the two. There are water stations set up throughout the course.
The 5K should be listed in your Personal Navigator for the
Castaway Cay day. That morning, anyone who is interested in particiapting will go to a designated area- one of the lounges, etc. and sign up. You will be given a numbered bib.
You leave the ship and take a tram to the starting point. The walkers/runners make two loops around the course and then cross the finish line. There is a race clock to show your time. Characters- usually Donald or Daisy cheer the racers on at the beginning and cheer them in at the finish. Cast Members hand out plastic "medals". They are circles that have Castaway Cay in the middle with black plastic ears on top. The red ribbons say WINNER.
Some people have also gotten certificates delivered to their rooms. Some groups have taken group pics with the characters before the race. There is also a Castaway Cay 5K race shirt available for purchase at the gift shop on the island only- not on the ship.
Hope that answers your questions! This is what I have found in my research, so if I am wrong, please correct me!
Wendy