I can answer on the use of single LNB camping dish for Direct TV for the 3 LNB High Def boxes. YES, it does work, you will just not get the HI Def channels, only standard definition. All the DTV standard def channels are on the 101 degree satellite, the other two LNBs are used for Hi Def and the majority of the specialty and foreign language channels which you may not be subscribed to anyway. You only need to shoot the 101 satellite, don't worry about the other two.
You 'may' have to go into the setup menu and tell the box you are on a single LNB antenna but probably not. Your mileage may vary, no warranty is expressed or given.
I use mine camping if I am going to be there for awhile. That being said, I don't at WDW, the cable and off the air is fine for me, I love me some Hanna Montana!LOL