December in switzerland with kids?

Planning a trip with 8 and 9 year old to swiss alps in late december. Itinerary is lucerne and either murren or wengen. It would be their first time to experience snow and want to know what kind of activities we can do in the area? how cold does it get?
If you have any suggested places to stay, that would be great. Would the swiss pass for trains be worth it i.e. 2 adults, 2 children? E.g. for train journey looking like: Zurich - Lucerne - Bern - Lucerne - Interlaken - Wengen - Zurich.

late december should be quite nice in the Alps. but do note that flatlands like Luzern and Zurich are not so nice in the winter - these areas are famous for their icy, foggy, gray winters. you may not see sun until noon. up high in the Alps, you'll get plenty of direct sunlight (weather permitting), usually 7-8 hours a day.

Murren and Wengen are both quite nice, both small, Alpine towns. they're on opposite sides of the Lauterbrunnen valley, perched on a shelf along the cliffs. Wengen has a more upscale feel, and very popular with the British. Murren is more down-to-earth, rustic (but it's most certainly a tourist town as well). Murren does get unobstructed views of the Eiger, Monch, and Jungfrau.

there should be snow by late december in the Alps. and unless there is some crazy warm front, they will make snow with machines during that time. a fun activity is tobagganing (or "sledging" as they call it there... look for the "schlittelweg" signs), great for young and old alike - no prior experience needed. there are lots of options in the Jungfrau area: Abendhubel-Murren (very, very pretty run), Wengernalp-Wengen, Mannlichen-Holenstein (about 7km - an exciting run), First-Grindelwald, etc. ask about it at the tourist office; they have a daily print-out of open tracks and snow conditions. you can rent the tobaggans in plenty of shops in the area; not too expensive... i think $10 for a day, but it becomes $25 for 3 days.

there is, of course, skiing. and there are also ski schools that will teach you and the young ones. note that the ski runs are not the same as the tobaggan runs (always check for the purple "Schlittelweg" sign). ice skating is available at the rinks (one in every town, at least). winter hiking is quite beautiful, especially after fresh snow. ask for hiking routes at the tourist office: they'll tell you what's difficult, intermediate, and beginner level paths.

Swiss Pass is probably not a good deal, since you pay by 4-, 8-, 12-, etc days at a time. truth is, if you're only going from Zurich to Wengen, it would be cheaper just to buy the round trip ticket - about 150CHF for 2nd class. unfortunately, there are 2 routes from Zurich to Wengen, and you have to choose either passing Bern or Luzern. so if you choose to go via Bern, you could jump off the train at Bern then hop back when you're ready to go to Wengen all in 1 day (and it still just costs the 150CHF RT ticket - make sense?). there is also a Swiss Card, which covers your roundtrip from the airport to the final destination; if going from Zurich to Wengen, it'll cost about the same as the normal RT 2nd class ticket. however, before you take the return journey back to Zurich, you can use this Swiss Card as a Half Fare Card (which gives you 50% off all trains, cable cars, buses, etc.)... this can be a significant saving depending on how many excursions you will make once in Wengen/Murren. (believe me, all those ski lift tickets and cable car rides can add up quickly if you're skiing or sledding.) alternatively, just wait until you get to Zurich - at the Flughafen, the people at the SBB service desk are very knowledgeable about the train fares; they can make a recommendation for you if you tell them your plans.