Roundtop, Whitetail, and Liberty are preparing to make snow but haven't started yet. Looks like there will be good snowmaking temperatures (at least at night) starting around Tuesday night. They haven't estimated an opening date yet, but I'm not sure I'd count on them being open by Dec. 1 -- maybe shortly after that.
Seven Springs is also making snow right now, and is hoping to open within the next week, so that's another possibility.
I think your best bet is Seven Springs. However, I'd wait until the absolute last minute before making a decision. If you look at the forecast, Whitetail/Liberty should get some good snowmaking weather, starting Tuesday. I've always been surprised at how fast Whitetail and Liberty mountain operations can make snow.
Also, both 7Springs and Wisp lie far enough west -"in the mid-Atlantic snowbelt" that they should also have some natural snow in the ground, which will make for a more "winter wonderland" setting, and not just "white strips" of snow thru otherwise bare ground. They have received snow last Friday, Friday night, and may receive more natural snowfall tuesday eve into Wednesday.