We have a worshiper who has Macular Degeneration and is having issues seeing the screen no matter where they sit.  I was wondering if there is an option to use a tablet to display a foldback screen that he can have with him.

While it wouldn't be wireless, you should be able to connect a regular monitor to the EW computer and run a display cable to it to accomplish this. You would need to assign a specific seat to them fight next to the EW computer for this to work well, but it is something to consider.