What the others have said is correct. Our whole family did the 5K on the June 4 Fantasy Eastern Caribbean. There were over 400 participants. We gathered in the Walt Disney Theatre with a meeting time of 9:15 am. The formal All Ashore was 9:45. We left the Walt Disney Theatre about 9:35 and walked to the the bicycle rental location. It got a little confusing, since regular folks and 5K folks were getting mixed together as we were leaving the ship. The start / finish is at the bicycle rental, which is where we got our bibs. The unsecured storage box was way too small for all the participants, so it was funny to see all the stuff just piled around it. I crossed the Start line at 10:13 am. I am a walker, so I finished at about 10:55 am. DW and I did some shopping for the 5K merchandise then headed back to the ship to change. Our DDs went for a bike ride afterwards with their friends. I believe the Western Caribbean has an earlier All Ashore, so the 5K would not eat into your day as much. I don't know about the 3 / 4 day All Ashore times.
As an aside, after DW and I were back on the ship for about 10 minutes, the skies opened up and it poured. We decided to have lunch in Cabanas, which was right at noon time. Our DDs arrived an hour or so later, dressed in garbage bags which a CM gave to their group to keep them dry. Because we did the 5K, we really did not get a chance to visit any more of the island for photo ops, etc. By the time the rain cleared and they allowed people off the ship later in the afternoon, it was late enough that we decided not to go back. We were very happy we did the 5K, and if we knew then what the day was going to be, we would still would have done the 5K. I only mention this, as if CC is an absolute that you want to do more of the island than just the 5K, check the weather reports to make sure you do get to enjoy it.
