Hi, Amanda!
Kudos to you for running the
Walt Disney World Marathon and congratulations on your upcoming cruise aboard the
Disney Dream! I was training for Disney's Princess Half Marathon earlier this year when I sailed on the Disney Dream the month before -- what a training site!
On Deck 4, the track goes all the way around the ship (.4 mile) -- which means that 2.5 times around is a mile. When I sailed, I -- along with a few other crazy runner types -- ran each morning, and I didn't even use my iPod! I do recommend running when the ship is moving. The air is cooler, and it's such a neat feeling to run as the ship moves. I've never been so fast!
On Castaway Cay, there is a 5K run on the island, and you can get a map from the Guest Relations or Port Adventures desk on board. I actually ran earlier that morning and was showered by the time we docked, or I would have loved to have run that route with the organized group. Yet, they did run it around 9 a.m. that morning which may be a little too warm since you're sailing in September.
I hope this helps you plan, and let me know if I can answer any other questions you may have. Have a wonderful day and a magical vacation. Bon voyage!
Andi