Hello moralon. Generally, a Swiss Half Fare Card works best for combined car and public transportation trips. You'd have to take three for the adults and the 17 year old. The other children travel along for free with the free STS Family Card. You can order here.If you plan to do more intensive traveling by public transportation, leaving your car at Interlaken, you can also take a look at the Regional-Pass Bernese Oberland (ordering can be done here).