Hello EuroTraveller34
The combination of the Swiss Half Fare Card and the Bernese Oberland Pass is a great fit. And for the rest of the days to use the Swiss Half Fare Card, together with Saver Day Passes or point-to-point tickets, does work as well. The Swiss Travel Pass is not very handy in the Bernese Oberland. As you will spend a lot of time there, it is certainly reasonable to focus on a pass that covers your needs there.
Please remember, there is the Swiss Family Card that comes for free for children 6 to 15.99 years, should children be part of your travel group. It also covers the Bernese Oberland Pass.
Best wishes,
Roland