I did NYE 2009-2010 at Magic Kingdom. We arrived at 6:30 AM for the 7:00 AM opening, left at 1:30 AM, and the wait for the buses back to the hotel put us back in our room after 3:00 AM. It was a long day but one of the most amazing days of my life, as it was always a dream come true for me to be at MK for New Years Eve.
Anyway, to answer your question about dining, my biggest suggestion, if you are planning to be there all day (which you have to be in order to guarantee that you'll be there for the midnight fireworks), is to book at least 2 sit down ADRs. We booked an 11:30 AM at The Plaza Restaurant which was a nice resting lunch, we took our time and relaxed for a good hour and a half before going back and braving the crowds again. Then I booked a 4:30 PM at Crystal Palace, which again was a nice break and gave us a ton of food to fuel up on before braving the longest part of the day- the period of time from the Castle Lighting to the midnight fireworks. We basically sat in one spot on Main Street from 6:15 PM until midnight, through 1 castle lighting, 2 spectro magic parades, one Holiday Wishes fireworks, one Fantasy in the Sky fireworks, and of course, the midnight fireworks. Amazing, but lonnnnnngggg. So I cannot over emphasize the importance of getting in two solid meals for lunch and dinner to gear you through the day.
PS if you want any other advice about spending NYE in Magic Kingdom, feel free to PM me as I'd love to share my experience and advice!