Hello Xackiechoic32
Welcome to the SBB Community.
All we can say, we already said in reply to the querries from fellow users:
https://community.sbb-tickets.cc/d/27152-swiss-travel-card-and-glacier-paradise-help-please/2
For the child with the Swiss Family Card, you will need a free-of-charge ticket that allows them to pass the turnstile. Ask at the ticket window for it.
And, most importantly: do not purchase mountain excursion tickets in advance. No local would do that. You may come from a country with 365 days of sunshine, it is not the case for our country; storms are possible at any time of the year. Get all the tickets once you arrived at Zermatt.
Here is a customer report of someone who purchased the tickets in advance:
https://community.sbb-tickets.cc/d/27612-glacier-paradise-cancellation
Kind regards,
Roland