Hello Jouyeagearr15
bought with half fare pass
You probably mean the Swiss Half Fare Card, as it is not granting any free travel like a pass.
With the (Swiss) Half Fare Card, you can purchase an Upgrade for a Day, or even route-based upgrades.
If you have got the Swiss Half Fare Card, the kids travel for free even in 1st class, as your class upgrade does cover them as well. If you do not have the Swiss Family Card, you need a class upgrade at half fare for them as well.
In the SBB Mobile App, or online, you have to select the discount in the passenger data first, see my instructions (screenshots) here:
https://community.sbb-tickets.cc/d/26418-how-can-i-save-the-info-of-swiss-half-fare-card/2
You can also get an upgrade from the counter, which is probably easier than dealing with the settings in the passenger data.
Does that make sense?
Kind regards,
Roland