D800 w/ 24-70 f2.8 or 50 f1.4 for Disneyland and Universal Studios Hollywood?

Personally i'd prefer the small and light 50mm over the pro-zoom.

However if you have the option, i'd purchase a Nikon 24-85mm f/3.5 - f/4.5 AF-S VR - that is the walk-around king and can be picked up pretty cheap at the mo!

Either that or Nikon 28mm f/1.8 AF-S if you want something that can go wide and get very creative in low-light. Although this wouldn't be my normal style of shooting, i would advise that at least with a wide prime on a D800 - you have plenty of resolution to crop out any unwanted scenery.

Number 1 choice for vacation though is the 24-85mm zoom!