If you are willing to make the extra trip and wish to avoid the crowds i would say roundtop they will have about 70% of their terrain open. But if you want some good skiing but more crowds with probably a good percent of their terrain open or almost open go to whitetail. Liberty is smaller and probably will have less open. I would say just keep checking the site or calling them (i have found that you get a more inside report when you call).
I used my voucher on saturday and it really feels nice paying nothing to ski! You will probably have great conditions (despite the rain) wherever you go.