Driving to Switzerland from Germany in early December, where should we go?

We have two very little ones, a 2 year old and a 6 month old. We dont have much more time in Europe and I was thinking about doing a drive to switzerland in Dec. Maybe a week there. I'm trying to find out what the best city for us to visit would be, but its hard because it would have to be somewhere we could take the kids and stroll. I'm thinking a bigger city with christmas festivals going on, someplace easy to drive to from the autobahn. Then from there take a train into the alps, maybe to visit a city at a higher elevation nearby. There has to be someplace like that someone familiar with the country would know of. I would love some advice! Thank you!