Itinerary and sights to see help

Unless you have a special reason,I would go straight to Lucerne upon landing. It's an easy 1+ hour train ride.
I would also stay in Pontressina instead of Chur, and maybe add a night. If you take the regional trains that run on the exact same tracks as the panoramic Bernina Express, you have more options schedule-wise and can get off at various stops to explore.
Have a wonderful time in this beautiful country!

https://community.ricksteves.com/travel-forum/trip-reports/lucerne-62eb4d28-60ab-4837-b4b4-91a2486eb732

Perhaps my Trip Report from 2021 will provide some helpful hints .

Also, if you add the countries to your title , you may receive more responses. Enjoy your adventures!

What time do you expect to land in Zurich? You can get straight from the airport to Luzern on a direct train in a little over an hour. That will leave more time for Luzern or Lugano.
Does your son have a car? He could pick you up at Oberriet station, just across the Rhine from Klaus. That will save going all the way to Feldkirch and back tracking on the S-Bahn.
I would not bother with a Eurail Pass. some sort of Swiss Travel Pass may be in order.

Pontresina is a beautiful town with houses decorated with painted motifs. Wonderful place to stay!

Thanks for suggesting to skip Zurich and go straight to Luzern.
Not sure why I would want to skip the Bernina Express- as I thought it would provide us a chance to see beautiful scenery versus going on regional trains. Am I missing something?

Is it possible to visit Jungfraujoch from Luzern?
How would you spend 4 days in Luzern?

You will not actually skip the Bernina Express if you take the Bernina Express bus from Lugano. This bus connects to the Bernina Express train at Tirano and you can get off at Pontresina. Stay there 2 nights rather than Chur. Then you can take a regular train that goes on the same tracks to Chur onward to Klaus.

Yes you can do the Junfraujoch, but it is both expensive and risky. By the time you et there from Luzern, it could have clouded up even if the day bean clear. The Swiss Travel Pass only gets you as far as Wengen for free and only a 25% discount thereafter, and a round trip from there will cost 160 CHF.

as I thought it would provide us a chance to see beautiful scenery versus going on regional trains. Am I missing something?

Yes, it is the same scenery, whether it is a regional train or a fancy Bernina Express train. The regional trains have windows you can open for a clear view and photos instead of fixed plexiglass.

How would you spend 4 days in Luzern?

Take a lake cruise and a ride up to the Rigi Kulm on the cogwheel train. With a Swiss Travel Pass, its is included, unlike the Jungfraujoch. You can go to Lugano on the Gotthard Panoramic Express, that starts with a boat ride across Lake Luzern to meet the 1st class Panoramic train to Lugano. Does require a seat reservation fee plus a class upgrade if you have 2nd class STP.

Thank you Sam for your help! Do you have a special internet site you recommend to better understand the trains? Each city has more than one station, so I get confused as to which station would put me closest to where I would be sleeping! We do not want to drag suitcases for a long journey, due to me not knowing how to use the trains properly! BTW- we have never traveled to Europe and used trains before, so we are pretty novice and ignorant.

Also do you have recommendations on finding hotels? Right now I have book refundable ones on Hotels.com, but after reading posts from other people it seems like we might get better prices we if booked directly with the hotel. Your thoughts?

PS- I grew up in Hales Corners, WI and graduated from UW-Madison. Yep a cheesehead loving Packer/Badger fan. :)

The Swiss rail site www.sbb.ch/en is not just a rail site, but a comprehensive intermodal transportation site for Switzerland, as such, it often lists ever bus and tram stop in a city. In general, just the town name is the name of the main train station. Zurich is "Zurich HB", and Basel has 2 important stations "Basel SBB" which is really the main station, and "Basel Bad", which is not a bad station, it is just short for Badischer Bahnhof. It is considered a German train station as it is included in the German local network tickets.

Pricing can be a little tricky, as it assumes you have a half fare card, so you have to double it top get the real price.

Regarding lodging, book asap, as records numbers of folks are going to Europe summer , folks who haven't crossed the pond since 2019. Safe travels!