Interlaken in Switzerland is a great base for a star type family trip. There is so much to do in the vicinity of an hour drive from Interlaken you could easily spend a week here nestled between the Alps and the lake.
Castle Oberhofen is located right on the lake providing amazing views, beautiful gardens and an interesting exhibit of historical furniture.
Strolling through the various historic rooms of our museum, you get a vivid impression of noble Bernese lifestyle from the 16th to 19th century. It's relative small size makes it great to explore with children.
And the gardens are pure joy - not too large, but so beautifully maintained and right on the lake..
The area is mostly accessible for visit in the extended summer months from May to October. Try to visit in June or September for a less crowded exprience. Here is a map of Interlaken and Lake Thun for your reference.