Seat reservations are uncommon on Swiss trains, and not possible on most anyway. So a free seat is one that has no person in it. In the rare case that a seat is reserved there will be a sign saying so.
The Children’s Co Travel Card (or the Junior Card) gives free travel for a child as long as the adult mentioned on the card is accompanying it, and the adult has a valid ticket or pass. The Child does not need anything extra.
Normal Point to Point tickets allow for stop overs. They are flexible, but limited to a route, whereas the Saver Day Pass is of course good for all public transport in the country.
However the Saver Day Pass is not refundable, and must be purchased in advance, whereas normal Point to Point tickets are refundable, and can be purchase even on the day of travel itself.