Hello Saidoumaf57
We show the adults’ Swiss Half Fare Card + valid adult tickets and Swiss Family Card (for kids)
Yes, for the kids, you do not need other documents than the Swiss Family Card plus their passport.
In Switzerland, there are no gates to access the platforms / trains; one can access the trains even without a ticket (although they risk a hefty fine for travelling without a valid ticket if caught on the train).
No, the trains are free seating. Fellow travellers often swap seats to allow a family to sit together. For us, using trains is like riding a bus in other countries. Hop on, find a seat, have a ride, hop off.
You do not have to free up seats if you hold a ticket for your kids. And the Swiss Family Card is their ticket. Certainly, when you ride a train or bus and an elderly person enters the bus or the train and is desperately looking for a seat, it is considered gentle to offer your own seat to the person.
Kind regards,
Roland