I see your itinerary is based on riding the Glacier Express from Zermatt to St. Moritz. Do you have reservations for that train already? They are required. If you do have them, I will proceed to talk about possible adjustments to your itinerary with that in mind, and hotels. But since you are questioning which pass is best, I am thinking you do not have your reservations yet. Or maybe you made “seat reservations only”, planning to buy the appropriate pass later.
If you do not have reservations on the glacier Express yet, I would like to suggest some changes in your itinerary that would have you travel on a different date. And point out how your choice of travel pass will apply to the Glacier Express. Here is the website for reservations:
https://www.glacierexpress.ch/en/
The website will show how many seats are available (I just looked at 2d class). July 26 is sold out, but there is a reasonable number of seats available July 27, 28, 29, and 30. Right now your itinerary has you riding the GE on the 30 (I think) so that is fine, but so would be a day or two earlier. I am going to suggest a change in your itinerary to put Luzern last, and go to the airport from there (unless your flight from Zurich is earlier than mid-morning). So a few days earlier would be OK too—-IF you do not already have your reservations.
As for which pass to choose, I looked at the cost for the GE with various passes. A seat reservation fee of 49 CHF applies no matter what pass you have. Without any pass, the ticket is 159 plus 49 for the reservation, so 208 CHF. Half Fare Card brings this down to 128 CHF, including the seat reservation. With a Swiss Pass, the total cost is the 49 CHF reservation fee. Your 13-year old will be free if you request a Family Card with the Pass, but will still pay the 49 CHF reservation fee.
Maybe this information will help you choose your best option for a pass—-It may well be the 15-day Swiss Pass.
So. . . . Please return and answer the question about your Glacier Express reservations, and then we can talk about your itinerary and hotels.
Since you need to decide on a pass before you make your GE reservations, that is the first step.