WE have just been to this one on the Brienzersee (other end of the lake from Interlaken) and I really liked it:-
www.aaregg.ch/
Its really clean, has a new toilet block with kids showers and sinks, family shower room a good playground. And its right on the lake in Brienz, has a beachy bit you can swim from. It doesn't have entertainment but does have a small (expensive) shop and restaurant.
Its not far from Geneva (maybe an hour) and the area has interesting thing to see apart from lakes and mountains.
Ballenberg is definitely worth a visit. Aareschlucht (a canyon) and waterfalls.
There are several campgrounds around the lac d'Annecy in France just over the border from Switzerland. ITs a beautiful area. Be careful as some are along a busy road.