Assuming you're wanting to stay in North America…
Quebec City is wonderful around Christmas. Old Quebec has a great Christmas feel, and you could pair it with Charlevoix if you want some skiing/outdoor stuff.
Stowe, VT is another one I'd look at. Similar vibe to Woodstock but better if skiing is part of the equation.
Whitefish, MT is also worth a look. Similar to Leavenworth.
Woodstock is a great option. If the goal is somewhere that really feels like Christmas, I'd have Woodstock and Quebec City pretty high on the list, with Stowe/Whitefish depending on how much skiing you want to work in.
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