One Week In Switzerland
 

In June, I'll be taking my two teens to Switzerland to meet my husband who will have been teaching a study abroad class in Milan. We'll spend 6 or 7 days in Switzerland. I'd prefer to not move hotels more than 3 times and am open to day trips from the hotels. I'd like a mix of museums, outdoor adventure and cultural experiences. I'd love to see a castle and take one of the scenic trains. I'll probably need to fly into Zurich or Geneva. What would you recommend for us to get a taste of Switzerland without spreading ourselves too thin? Thank you

Stay in Grindelwald and take day trips from there. Why? Grindelwald offers lots of outdoor activities for teens. You can do a day trip to Thun to see a gorgeous old town with an imposing castle. For your last evening, stay in Zurich or Lucerne and enjoy the city.

Moving three times in just 6 or 7 days seems like too much. I suggest cutting the max down to two. Thun makes a good base as it's easy and fairly quick to get from there to Bern, a lovely city, or to Interlaken onwards to Wengen, Grindelwald, etc (Bern is 20 to 30 minutes from Thun depending on train; from Thun to Interlaken it takes about 30 minutes on the direct train). Plus there are lake cruises that start right in Thun. https://www.interlaken.ch/en/experie...s-on-lake-thun Thun gives you plenty of easy-access options for both fair and rainy weather. From Thun it's also only 40 minutes by direct train to Kandersteg, a lovely village not as heavily touristed as the villages around Interlaken.
For your husband, there are regular direct trains from Milano Centrale to Thun, the journey takes about 2 hours and 45 minutes.

If, for some reason, it's a really hot day (you don't say whether your trip is in early or late June), Wengen has a great outdoor swimming pool in a very scenic location. A good way to cool off for a few hours and take in the mountain peaks.

We like Zurich a lot and go there pretty often -- we have two nights booked in the city next month before heading off to Vienna on the railjet train. Can recommend some good Italian and Asian restaurants in Zurich if you decide you want a night without traditional Swiss cuisine. Plenty to do in and around Zurich. Your teens could even take a kayaking lesson right in town ...

Where will you fly in: MXP. ZRH, GVA?

Leaning towards Geneva and Zurich is an option

Oh, there are many possibilities in Switzerland! How about spending a few days in Montreux and visiting Chillon Castle, then heading to the mountains in Grindelwald and topping it off with a trip to Zermatt?

This is good (Swiss_Sights) except that Zermatt is out of the way and will use up two nights and a day. You could skip Zurich and fly round trip to Geneva but I prefer Zurich over Geneva. How about an open jaw flight like this:

Fly into Zurich, spend one night
Train to Grindelwald or Thun, 3 nights
Golden Pass train to Montreux, 2 nights
Train to Geneva, one night and depart

That's seven nights and it will be easy to fill those days.

Zermatt wouldn't be more "out of the way" than Bernese Oberland, but all depends on the place the OP will fly in to.