As I live in the middle of the Cairngorm National Park . I can tell you that this year we had snow in the valley for about six weeks around Christmas . My wife who travels to Inverness every day in a Volvo V40 (45 miles) only missed 3 days and worked from home. The main roads were fine , it was the track we live up that I had to tow her in and out most days. I was using a 20 year old KZJ70 , and with snow about 18 inches in places and I never got stuck.
I notice you have a BMW AUTO, I would not use that here if you want to go exploring , as the minor roads are not treated. There was not enough snow to justify using chains, and unlike in Europe in is not legal requirement to carry them.
The areas where the tourist go ie the ski areas were all kept clear or the snow gates were closed preventing anybody from using the roads.
As far as accommodation goes there is a large choice, all depends on your requirements, and budget. Aviemore is expensive. There are many small B & B's about in surrounding villages,just look on the net. If you want more info on an area or accommodation I am sure I can find out for you. Where I live the nearest village many of the houses are rented out as they are second homes. The good thing here is that the eating and drinking places are welcoming to everyone with kids and dogs.
Garry