Hello Steel Daddy
Firstly, welcome to the SBB Community. We are a customer support forum run by volunteers.
Just enter the route in the trip planner at www.sbb.ch/en. Enter all passengers using the pen icon. Or use the SBB Mobile app instead.
The ticketing system will probably come up with 3x Saver Day Passes, and 1 Day Pass for Children (up to 15.99 years of age). For the way back, you could also purchase Supersaver tickets.
Do not purchase Supersaver tickets for Geneva to Zermatt when directly arriving by air; Supersaver tickets become invalid if you miss the train departure as indicated on the ticket. The Saver Day Pass is valid for any departure on the day of validity and, in most cases, the best bargain. Its price is raising the nearer the travel date and the higher the demand.
Kind regards,
Roland