Hello NewYorkFamily
For the trips listed above, I would choose the Jungfrau Travel Pass.
https://www.jungfrau.ch/de-ch/jungfrau-travel-pass/
For the travel to/from Interlaken, you could purchase Point-to-point tickets, or a Saver Day Pass, whatever is cheaper for the day of travel. See www.sbb.ch/en or download the SBB Mobile app. For the children, you could definitely purchase the Day Pass for Children which is CHF 19 per day/child, granting unlimited travel on the Swiss public transport network, just as the Saver Day Pass.
https://www.sbb.ch/en/tickets-offers/tickets/day-passes/saver-day-pass.html
https://www.sbb.ch/en/tickets-offers/tickets/day-passes/day-pass-children.html
Interlaken is a great travel hub, yet it is not in the Jungfrau area (you will have to commute o the area every day), and Interlaken is very famous among tourists from the Middle East, Asia, and India.
Kind