Thanks for the pep talk dis-runners. I almost pulled the plug on my Sunday volunteer shift. I just didn't want to be subjected to the extra harassment likely to come.
If you are likely to worry about things don't read my next advice.
Corrals Sunday are likely to be over stuffed and 'normal' crowded running conditions are likely to be exacerbated.
You will likely have half runners with you who will want to go out much faster than you should run your marathon. Run your pace.
Adding more runners to the course may stress food and water stations. Hopefully cool temps will keep this in check.
If Half runners bandit the second half of the full course, and accept full medals, Disney could run out of Full-Marathon-medals. I would expect to see some type of policing or halting of half bibs past the 13.1 mile marker. If people handing out medals don't give ½ runners a full medal, let it go. There are only enough medals for people who signed up for the full, Goofy and Dopey. Disney may have this completely covered this time. From over fifteen years of experience, my observation is they usually get new things wrong the first time.
Garbage bags make great windbreakers and ground cover. I would be going for this type of 'gear' over last minute trips to the expo. Ask a maintenance/room-service person for a bag or two.
Good luck, enjoy your Marathon. I would be neglecting my volunteer oath if I didn't say, "You're almost there."