Hi Ghiboiloa19
So I understand correctly, that all adults have a Swiss Half-fare card, correct?
If so, you can request a Swiss Family Card at any ticket counter from the SBB or directly where you bought the Half fare passes from.
With that, children will travel for free, as long as you (the parents) have a valid ticket.
If the children are under 6 years of age, you don’t need to apply for anything, they travel for free.
Hope this clears some things up.