Seven Days in Dec/Jan with my sons...where to start?! ;-)

Before you go any further, go to Booking.com and peruse accommodations. I'm concerned about your budget, and there is no substitute for looking at actual prices and options. That might affect which places you choose and will certainly give you some direction. good luck!

Thank you! I've actually just had a very quick look through the Lauterbrunnen area and realise that USD200 isn't going to make the grade ;-) I'll alter my original post...thank you again!

Note its ski and winter sport season so things get busy and accommodations for short stays in scenic places may be an issue. All places in the mountains are hit or miss due to weather, and a day that starts out sunny can turn cloudy and vice versa. Scenic train routes are also covered by regular trains so the "name" trains are not worth it of you're on a budget.

My standard suggestion for people who've never been and have limited time, is to go to Luzern, a lovely city with a cruisable lake setting and three+ mountains you can go up and find recreation activities as well as great views (weather cooperating. And Luzern can be reached by train from (and to) the Zurich airport rail station in about 1.25 hours.

Just be prepared for high prices for everything. I still think about the hamburger and soda I had for 32CHF. The Rick Steves Guidebook has a lot of good recommendations for budgeting and transportation discounts.

winter kayaking on Lake Brienz, one or more of the many train / cable car trips to mountain views, and boat trips on some of the beautiful lakes. My future Physicist son is also keen to visit Bern (perhaps as a day trip) and see the Einstein statues ;-) A castle or two would also be fantastic as my boys have never seen one before!

Less expensive for accommodation than in the Lauterbrunnen valley, but close by are:

Wilderswil - you can see a list of hotels and prices here to help you compare

Meiringen - especially if you have Sherlock Holmes fans

All the little villages along the Lake of Thun, including Spiez and Thun, or along the Lake of Brienz (such as Bönigen)

Here are some other money saving accommodation ideas from Switzerland Tourism

Schloss Thun is impressive from the outside, has a descent exhibit and you can climb up into each of the four towers to look out at the view.

Going up the Schilthorn is free on your birthday

Is the Matterhorn often behind the clouds? I have gone there about six different times and have always seen it, so I started to wonder. Found that they actually take a photo every day of the year. You can find them here and see what you think.

Research hotels on booking.com, but then email your selected hotels and book directly, which usually results in a discount. I did this with Hotel Bellevue in Murren, which has a fabulous view. Ruth, the owner/ manager, communicates promptly in English. I'd also book asap.
I'd agree that staying in the Berner Oberland for much of your trip would be a great plan, with some time in Lucerne.
Happy adventures.

Thank you all so much for your time and expertise! I really appreciate it :-)

I am curious -for the original author - what did you end up deciding? (Same last minute trip here)
I’m very concerned about accommodations!

Hello!
We've decided to have 3 nights in Lauterbrunnen via Bern for the day, followed by a night in Chur before heading on the Bernina railway to Tirano for a night, then 2 nights in Lucerne before leaving from Zurich.

We were quite limited not just with the cost of accommodation, but the availability so it's taken many late nights of playing tetris with the calendar to get everything to fit. We were able to find reasonably priced rooms at the Hotel Oberland and also in Lucerne which helped a lot.

Getting so excited now!