Mousetraps set with chocolate as the bait.
Paper/hessian sacks are the best to keep potatoes in.
With regard to hanging the sacks from the rafters, its amazing where mice can get, the little swines!!
Storing the potatoes in a clamp, I would say that your sandy soil is ideal for the purpose.
Either way, if you keep them in your garage, it's goin to be an enormous infestation of mice that is going to eat the whole crop.
valmarg