Hello RamArav
Welcome.
I just told you what we, the Swiss, do when planning mountain excursions. We wait for the weather forecast which is not reliable more than 2 days out.
Yes, you can save the half fare option while doing a dummy booking. The app keeps the setting for your next purchase even if you do not complete the dummy booking.
On tab Profile, you can add co-passengers, for example other adults being part of your group, and then you can purchase tickets for them, too, and all in one stop. The Half Fare option is available for them, too.
Simply kerp in mind that e-ticket and mobile tickets need your physical ID card or passport (no photos, no copies).
Best wishes,
Roland