I really don’t know how you will be able to do this without compromising the appearance of the potatoes (the skin will wrinkle after 2 hours, never seen them after a full meal period of 3 hours) or the food safety issues (hot food hot, cold food cold and the danger zone is in between). The only thing coming close in advance preparation of the potatoes would be warming or holding cabinets, as used by catering companies, hotels or hospitals for delivery of food from commissaries. These still need to be plugged in. They can keep product warm or even slow cook things. Here is a link with some examples.

Unfortunately, I think you may be out of luck…