We really enjoyed staying in Sebastian's chalet, grandparents and kids all gelled in the house. Particular benefits:
+ Flexible space
+ Two sitting rooms (english TV a bonus for the kids)
+ Wifi
+ Spacious and well equipped kitchen with good size fridge / freezer
+ good sized bedrooms
+ Bathrooms all newly renovated and plenty of hot water
Only cautions: Lighting is not very bright, and it's 100m above the cantonal road. We didn't find noise from cars an issue in practice but on weekends you may get a few motorbikers. Being Switzerland however nobody is driving fast and it's all very orderly. There's a lane below the chalet allowing you to walk into rossiniere without having to to walk the 200m section of cantonal road into the village which does not have a pavement.
It was a great value stay for us despite the painful £ / CHF ratio for other purchases, and the area is beautiful. We did the following in a week:
+ Walks: mountain walks and the flat walk around the lake below Rossiniere. Check out the mountain herb farm 'Les Jardins de La Tour' high above the chalet with unique monorail for bringing the herbs down, they also have their own products and a good web site. On Fridays they do a walk around their gardens.
+ Walk around Lauenen lake and lunch at the restaurant there (good suggestion by Sebastian)
+ Glacier 3000 - good way to spend half a day and decent value with swiss half fare rail pass, we also used the rail pass to go across switzerland with the 'transit' pass (contact swiss tourist office in Covent Garden, very helpful) and up to Kleine Scheidegg in Wengen for a day trip
+ check out Michel Beroud (fromagerie) and butcher (best veal in the world), both in Rougemont
+ the panoramic train to Montreux for a day, and stand up paddleboarding on the lake
We also enjoyed lunch at Hotel Elite, unpretentious food at fair price prepared and served with real care. And of course there's Gstaad for those who live the ritzier life than us.