Places to go, things to do BY CAR within 1 Hour of Interlaken

Don't rent a car. It will only add expense and in turn limit what you can do. If you come by car to Interlaken the best thing you can do is leave it in the car park the whole time. But if you rent a car only to go from the Airport to Interlaken you are a lot better off not doing that in the first place.

Most of the interesting things to do in the area involve making interesting loops using the local stransrpot. Eg. taking a boat to Briernz and the train back. Or walking the Lauterbrunnen valley one way, and then returning via Mürren. Or going up the Jungfraujoch via Grindelwald, and returning via Wengen...

If you want to do adventure style things, like Paragliding and/or rafting the companies that organize those will all pick you up at your accommodation. Your kids can eg. go paragliding while you go on a boat cruise...
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Great advice by Wengen, and taking a boat to Brienz and a train back (or vice-versa) is a great idea. You won't want a car to get around in those towns, anyway. Much easier to walk.

There is a lot of parasailing around Interlaken. They actually land on a big field in town. In Brienz, there's the Rothorn Bahn, a cog railway that goes to the top of the mountain. Beautiful views. The Rothorn terminal is across the street from the train station or the boat dock. If you took the boat toward Brienz, the boat will stop at Geissbach Falls. I've never done it, but there's a tram or something going up the hill. Then you take the next boat back. Not an adventure, more of a scenic visit, though.

Oh yeah, if you're in Interlaken, we like a pub called Brassiere 17. Just an ordinary, old pub with good pub food. Live music on some nights I believe. On Rosenstrasse 17, a short walk from the Interlaken West train station.

I like the Brasserie 17 (mind the spelling, Brassiere is something else:-) )
I always go there on my birthday, as in November they have Belgian style Moules Frites, but I go there at other times as well. The owner is Dutch, and the place has definite Dutch "Bruine Kroeg" vibes.

There are other nice restaurants as well. A3 near Interlaken Ost (in the youth hostel) is good for lunch. Just look at places that have pictures on their menu and avoid those.