The 30-day Half Fare Card almost always results in the most savings, but you do have to purchase tickets for each journey. Just the journeys you outline amount to about 314 CHF worth of full fare tickets per person. With a Half Fare Card costing 120 CHF, your costs will be 277 CHF. A 15-day Swiss Travel Pass is 485 CHF, so you can see you will be paying quite a premium for the convenience of a pass.
Now how many little side trips you plan on will add to that. The trip to the Schilthorn from Muerren is covered by the Swiss Travel Pass. But other mountain lifts only give a 50% discount, like the Gornergratbahn in Zermatt. The Jungfraujochbahn above Wengen only gives 25% discount. The Half Fare Card always gives a 50% discount for everything, mountain lifts, boats, city buses and trams.