Question on Swiss Saver Flexi Pass

We will be spending 6 days in Grindelwald in the first week of June. To keep our itinerary flexible to change depending on the whims of weather we have chosen a Swiss Saver Flexi Pass 4 days. We are a family of 2 adults + 1 kid (9 years)
I am being told by my local travel agent that all the 4 days we plan to use the free travel options needs to be pre-decided before departure from the country of origin.
Can somebody knowledgeable please confirm this?
Thanks in advance.
Shibatosh

Hi Shibatosh,

Well, normally you only need to choose the first free travel day when buying your pass. The Swiss Saver Flexi Pass is meant to allow flexible traveling and thus choose your days on the spot like you assumed. As far as I know, you travel agent should be able to leave the other dates on the pass blank.