second the eastern or western plateaus of the canyon (though Kolob Reservoir Rd may not be open) and while you're up there spend at least a day at Bryce (likely much more snow). The hike up to Observation Point won't be as treacherous as Angel's Landing for a 'view from the top' but bring some rope & crampons just in case. Nearly a new moon so star trail opportunities exist... If you've never been to Zion, spend some time early on scoping the valley up to the narrows and absolutely check out East Zion. I'm hoping to get up there or to monument valley over Christmas.