Daveskib,
My chinese elms still have green leaves too, although I am in Charlotte, NC area. Most of the leaves, though green, are dormant, but haven't fallen off yet. I have started mulching my trees into their outdoor wintering bed, some with leaves still on. We haven't had much more than a couple of light frosts here. Have you had any hard frosts or freezes yet in Delaware? If so, I would think that the leaves are pretty much dormant, just not smart enough to fall off.
I would prefer that the trees have no leaves on them before placing them in winter storage to remove the possibility of overwintering fugus and stuff, but I want to protect the roots more than I worry about the remaining leaves. I would assume that the same would hold true for you, even in the enclosed area of the unheated garage.
I do not think that lack of light on the existing leaves will cause any problems to your trees, if that is your concern.
Regards,
Martin