Mmmm I've found a way better option! The Duved/Åre area is still pretty far north and snowy. :)
For example on 27th December:
- ICD Rotterdam C - Amersfoort C 07:11 - 08:20
- IC Amersfoort - Osnabrück Hbf 08:36 - 10:51
- ICE Osnabrück Hbf - Hamburg Hbf 11:23 - 13:14
- margin for German delays, time for lunch
- EC Hamburg Hbf - Copenhagen 14:56 - 19:38
- night in Copenhagen or Malmö
On 28th December:
- frequent Copenhagen - Malmö train
- X2 Malmö C - Stockholm C every hour
On 30th December:
- night train Stockholm C - Åre or Duved 22:39 - 08:15 (book ASAP)
And the return… night train Stockholm C - Hamburg if available. Otherwise similar route as the way in.
I haven't looked at accommodation or activities, that's your job but I'm sure you can find some things to do!