it gets very cold up here in minnesota but that doesn't seem to bother the actual big maples in my yard.
You touch on a very good point. The reason the trees in your yard are OK is the fact that the roots are protected. The branches, once dormant, are very hardy if the roots are protected.
There are several options available to you. You can un-pot them and bury the root-ball. You can bury the pots and all. You can set the pots on the ground and mulch. Or, you can bring them into an unheated garage after they are fully dormant. The one thing I would not do is to simply leave the pots outside, exposed.
I don't fertilize dormant deciduous trees but you can still fertilize now. If they are outside I don't need to water. If inside the garage watering will be required periodically but not as often as in other seasons.