Hello Right Person
There is no difference in terms of validity. And both are for tourists.
The Swiss Family Card is a complimentary ticket that is given for free when purchasing the Swiss Travel Pass or the Swiss Half Fare Card; the Swiss Family Card is not for purchase, it is valid for 30 days.
Those who neither purchase the Swiss Travel Pass nor the Swiss Half Fare Card can purchase the Junior Card for CHF 30 per child, valid for 1 year. It is a paper ticket that can only be purchased at a train station’s travel office.
Does that make sense?
Kind regards,
Roland