how to get to Minakami from Tokyo

I want to take my 78 years old mum to Japan for the 1st time. She also wants to see snow for the Ist time.
Searching the web I think Minakami will be a nice place for her to experience Japan and snow.
My mum is old and is not strong enough for long walk so i want to get a place where is easy for her mobility. Place where she can experience snow without having to walk long distance. Places which are easily accessible by train or bus.
I hope some one can give good advice and direction
Thank you

When?

Access and Orientation:

http://www.japan-guide.com/e/e7461.html

You might want to consider Karuizawa Prince Ski Resort :

KARUIZAWA BY TRAIN:
From Tokyo Station, take the Nagano bullet train and get off at Karuizawa (60 min.). The resort is located outside the south exit.
The ski area is 1 minute by taxi or 10 minutes on foot.
A free shuttle bus between the station and ski area is also available.

http://www.princehotels.com/en/ski/karuizawa/access.html

http://www.japan-guide.com/e/e6032.html

One of the easiest place would be Gala Yuzawa. Shinkansen trains arrive at the front of this ski resort, i.e., 0 min on foot.
http://www.galaresort.jp/winter/

In winter, snow is everywhere at the north part of Japan, especially just at the west side of the central mountains. Karuizawa is situated at far from the Japan sea, meaning lack of snow. Usually Karuizawa's snow is made by snow machines. Minakami's one should be natural, but still at the Pacific Ocean side of the mountains. If you prefer non-ski resort, Yuzawa onsen, at the foot of Gala Yuzawa, would be better than Minakami and Karuizawa.

http://www.japan-guide.com/e/e2265.html

Thank you very much for all the advice and recommendations