If you're feeling up to it, you can simply boil the potatoes in their skins. When you want to mash them, the skins slip off easy as anything and the spuds taste more spuddy for it. Knocks a task off the list and you don't have to worry about storage space for them, or how to store.

Ina Garten also isn't afraid to make mashed potatoes the day before. Here is how she does it (with another suggestion in the comments section): https://food52.com/blog/11742-ina-garten-s-make-ahead-thanksgiving-advice

Yes, of course! No salt required. They'll hold just fine.