Re: shrink wrapping
As noted your batteries should come out for the winter or at the very least have a trickle charger connected. If not they will freeze over the winter. (experience speaking on this one). Also top the water up in the batteries, if you can, with distilled water, not tap water. Standard maintenance like cleaning etc is also easier to do in the garage where there is room.
The covers should also come in for the winter and one of the best options I have heard, is to put a clean sheet between each one, especially if they have windows and role them up. Do not fold or bend since the windows will not take well to being creased for a extended period. The sheets prevent the windows from sticking to each other and leaving marks or worse getting ripped when you seperate them in the spring.
Make sure to clean the covers first of course and maybe even weather protect them to the manufacture of the materials specifications.