Jul 11, 2017 - 5:10 PM
in reply to jill77
Hi Jill77 and welcome to MySwissAlps!
You will want to look at the Jungfrau Travel Pass I think. Read all about the pass, what it covers, for how long and for how much here. You can buy a Jungfrau Travel Pass for your 6 year old for only 30chf.
The motorway vignette issue is explained here (and not connected to cable cars or the Swiss Half Fare Card). If you are renting a car in Switzerland it most likely has the vignette already.
To know for sure you need to figure out what trips you will be taking in the Jungfrau region by train, cable car, boat,bus etc. and compare to the Jungfrau Travel Pass - we have an excel sheet here to help you do the math.