Hi Hodge29 -
Welcome to My Swiss Alps.
<<"After doing some initial research we have been bombarded by information and can't really decide what we want to do in 6-7 days, there's so much to do and so much to see,">>
I've been visiting Switzerland since 1980 and still have not run out of new things to do.
It certainly is a serious problem, but luckily it is a nice problem to have. ;-)
A reasonable first time itinerary would be to spend about half of your time based in or near Luzern and about half your time in the Jungfrau region. ( Luzern is in the German speaking region, so you will see that spelling on the road and rail signs. )
The choice is made more difficult by the time of year.
October is a transition month between seasons in the high alps, and, by the end of the month, tourist services are being cut back for maintenance of various facilities, some hotels and restaurants will be closing until early to mid-December, when the ski season starts in earnest. The early part of the month is usually quite nice in those regions.
When in October will you be traveling?
Since you will presumably not be jet-lagged, you don't need to take the first couple of days to become accommodated to the time zone. I'd tend to head directly for one of the mountain towns immediately upon arrival. Weather changes suddenly in the Alps, and is difficult to predict accurately more than a day or so in advance. Staying for a few days is the best way to make sure that you have clear weather to go up to the Jungfrau. Wengen and Mürren are nice, Lauterbrunnen and nearby villages are on the valley floor and convenient for travel out of the region or up to Schilthorn or Wengen and the Jungfrau.
Grindelwald is a bit more commercial, more stores, etc..
Interlaken is a good transport hub, but not much of a tourist destination in its own right.
All are enjoyable. I prefer Wengen. In case you have not been bombarded by enough information, you may find this report of value. I do.
If you were jet lagged, or at other times of the year, I'd start with the one hour train ride from the airport to Luzern immediately upon arrival, take advantage of the wide range of geography and things to do and see at a leisurely pace, then go onward to the Bernese Oberland near the Jungfrau.
I'd have to work to figure out the best way to fit in the Glacier Express....see below.
Zürich is easily accessible from Luzern with frequent train service. I like it a lot , but more for cultural activities than for scenic attractions.
That would let you do everything you list except the Glacier Express. it would require about a day or more to access it, ride it, and get back to the bases described. If it is a must, then some more planning with the timetable would be critical.
Please check schedules. I may be mistaken, but I vaguely recall a gap in service each year ....perhaps in October....
You could reach the Rhine Falls from Zürich or Luzern, but, in my personal opinion, it should be ( as you note) an option, and I personally would not exercise the option considering your other proposed activities and locations.
To help with further guidance, it would help us to know a bit more detail about your interests beyond what you have mentioned. For example, some people go to Switzerland just to ride the trains; destinations are secondary for them.
Trekking? Train rides? Museums? Old towns? High mountains?
Luzern offer all of those, which is why it is a good starting point for first time visitors.
If you have not yet found it, this map is particularly good for travel. Under Points of Interest/Traffic in the menus, you can turn on icons for train and other transport stations, for example.
The time table is invaluable. Dig into it. Lots of good stuff buried in in it.
Hope that gets you started.