Yes, when it warms up to the level of cold that the trees have successfully tolerated in past winters, I would uncover them. They are dormant, so there isn't a lot of photosynthesis going on right now. But the bark should be exposed to the air and light, I think. If it's going to be windy, I would keep them covered, or at least in a spot protected from the wind. Wind can desiccate the plant and cause significant damage, because the roots can't absorb water from frozen soil.
It's difficult for me to offer suggestions about how to treat the trees after the very cold weather ends, as I don't know where you're located. This is an international forum, with members from all over the world. If you want to share the area where you're located, it would enable me and our other members to give more accurate responses to your questions. Many of our members list their by using their USDA Plant Hardiness Zone number as part of their profile. Since I don't even know what country you're in, the best help I can offer, I think, is the link to Wikipedia's article on the subject. The article contains links to determine your zone number if you're in North America, Europe, or Australia.