I concur with the recommendations to bring a mid range zoom. I recently went through my shots of my last trip to WDW, and a number of my shots were taken with my 24-70 f/2.8. Personally I would also bring an UWA as WDW provides numerous opportunities for wide angle shots.
I know many folks do not want to bring their telephoto zoom lenses because of the weight...but I'm not one of them. When watching parades or shows like Fantasmic, I often like to use my zoom. The safari ride at Animal Kingdom is another opportunity where I really want a lens with some reach. Therefore I will bring two telephoto zooms with me, although I won't necessarily carry them both around with me 24/7.
Lastly, I love dark ride shots so I will definitely bring a fast prime. I am looking forward to trying out my new Sigma 35mm f/1.4.