Glacier Express and Bernina Express with 1 week in Switzerland

If you like riding around on trains in Switzerland, sounds very doable.
Rather than going to Davos, not all that attractive large town (been there several times for skiing, which is great), think about going only as far as Filisur. There is a trail down to the base of the Landwasser Viaduct for photos. You've seen pics many times, it is a travel poster favorite, and you will have passed over it on the Glacier Express. But it will be gone in 30 seconds. This way you can ogle to your hearts content and it is way better view than from the train.

Lugano back to Zurich, instead of using the new Gothard Base Tunnel, which goes completely under the high Alps, take the Gothard Panorama Express which uses the older route mostly over the Alps, includes a boat ride for the last leg to Luzern. From Luzern, you can get a direct train to Zurich Airport in the morning for your flight home. It is just over an hour away.

By then, your mountain rail Jones should be pretty well satisfied.

The train part is definitely doable, the bus part will depend on if you manage to get the reservation you need.

Thank you for the input...I like the idea of taking the trail down to the base of the viaduct and the more scenic route back to Zurich.

Steve