Also, earlier in the week there was a discussion about doing the Dopey for the first time. This year was my first Dopey, and first ever marathon. Some of the information I found most valuable when I was training was not about running, but planning the weekend.
First off, we agreed to a nice slow pace for each race, even the 5K. I made pacing bracelets to wear with upper and lower limits. At each mile marker, we were able to look at the bracelet and determine if we needed to pick it up or pull back a bit. Slowing down for the 5K was tough.
Second, make a fueling plan based on what you discovered during training. If you know you need to eat every four miles to maintain level energy, eat every four miles, even if you don't feel like it at the time.
Thirdly, after each run we would put our feet up. Literally, lay in bed with our feet in the air resting against the wall. I enjoyed this particularly since my feet get really tired and my feet and ankles swell.
Fourth, pool time and hot tubbing. Spending some time in the cool pool, relaxing, was very refreshing for the legs. And the hot tub does wonders for relaxing the legs.
Fifth, even though you are at WDW, try to limit your park time until after the marathon. We would walk to dinner (table service to be sure we had 'healthy' options), pick one or two things to do, but otherwise we would relax.
Finally, remember you are doing this because its fun! Enjoy the atmosphere, and stay calm. We stopped for pictures when there was a character we were interested in, stopped and the petting zoo, and overall just had a fun time.
That was longer than I intended, but the information was so helpful for us this year, I thought it was important to share with other soon to be christened Dopeys!