Thank you so very much Annika on your insightful response! I'm truly grateful for all that help! I'll just share some more info on our itinerary if that helps :)
Firstly, we'll be staying at hotel Leoneck.
August 4/7: For one of the days in zurich, we plan on visiting the Rhine falls (passing and stopping briefly at scaffenhousen on the way) and probably go for a boat trip on the falls. We were hoping we could also go up a hike up utielberg the same day but I just read your response on my other post (thank you so much for it!) and I guess you're right.. It might not be possible.. But just Rhine falls for the whole day might leave us quite a few hours on our hands.. What would you suggest doing after the Rhine falls..? Also, when would be best to visit the Rhine falls?
August 6 (interlaken) : we hope to cover quite a lot here and hence we'll end up using the rail system extensively! Reichenbach falls (or would it be more feasible to fit in Giessbach fall instead) , aare gorge (or should we go to lake thun/brienz instead), harder kulm, rosenlaui glacier George. (If I take interlaken ost as the starting and end point for my journey, how should I sequence the places?)
August 4/7 : following your help on the other post for which I'm highly obliged, we plan to go on a boat trip on lake zurich, old town (including the famous churches) Bahnhofstrasse, and lindenhof. (Is this too less for a whole day? Should we add more?)
We haven't got the cost of traveling from zurich to interlaken, that's under control of the agency..
So looking at this, what should we go with? 4 half fare cards for the parents and teens and the free Swiss family card seems like a nice option but I just checked the price after it becomes really costly then, so would it be better to go for a all zone ZVV card for the Rhine falls day and a a centre-only ZVV card for the other day? But in this case, would we have to get these cards for the children too? If so I might consider opting the junior travelcard.. One purchase is enough for both the kids (10, 8)? And how'd we manage reducing costs in interlaken then?
Oh and We've heard that the aufsehen festival shall be going on during those days? Is there anything special we should consider doing/seeing then?
Finally, please suggest some budget friendly ideas for gifts to get back home for family and friends from zurich!
I understand my reply got really long and heartily apologize, but I'd be really grateful if I could get the help I need, since we doubt we'd ever return to Switzerland (although I hope I really do!) and I want to make it the best thing ever for both me and my family :)