This Christmas me and my wife will be taking a trip to Switzerland we will be there from Dac 19- 29th. Our 18 month old son will be with us. We are already finding it difficult to figure out what to see with the time we have. Among other things we are trying to figure out whether we should spend time in Berne or the Jungfrau Region. It will be winter and neither one of us are skiiers, we are mostly in scenic and historical/culture sights. Given the time of year i don't know if Jungfrau region is better done in the warmer months.
Since neither one of you are skiers, at that time of year my suggestion would be a stay in Lucerne.
With 10 days in December, and if you are staying in Luzern, I would suggest a day trip to Basel (1½ hours from Luzern by train) to see the Christmas market, the largest one in Switzerland. Your 18 month old should enjoy this. This stays open in the evening as well.
From Luzern you can to boat trips on the lake. They run a limited number of boats in winter, and it could be cold if it is windy.
Take the train to Interlaken, this is a "poor man's glacier express". Lots of views over snowy landscapes and down to lakes below you. 1-2 hours in Interlaken, then if you started early enough you can move on to Bern in the afternoon, and take a direct train back to Luzern.
Don't forget the days are short, it will start getting dark around 4:30.
The train from Bern to Interlaken is pretty good too, it's just not the total Alpine experience you get south of Interlaken.
I thought Bern was a great city and would go back in a heartbeat. Good size, walking districts, very good tram system, nice train station. And bears! Don't know if they are outside during the winter.
The bears hibernate in winter.