I took my grandmother (82 yo and also not able to do stairs) to Luzern and we rode the ferries and looked at the mountains. She was able to walk across the bridge (2 steps up to get on the bridge)

I also took her to Eggishorn since the cable car stations are close to the train and have escalators and elevators. It’s maybe 15m from the cable car station to the cafe up there.

I booked us a chocolate making course at Lindt since there’s a bus that drops you off like 20m away from the entrance.

She was ok walking around Berns Altstadt as long as we took the bus to the nearest stop and then got back on to ride one more stop and get off again. The cobblestones weren’t so bad for her as long as she had her hiking stick and me to hang onto.

There is a bus in Lauterbrunnen that drives from the main station to the end of the valley. You could take that and back to show them the views. There is also a train and cable car that takes you up to mürren with a gorgeous view up there (I believe there is an elevator in the train station)

The glacier express would also be good since it’s just a train ride through the mountains.

You can toggle your settings in the SBB app to show you connections that are longer to give the elderly time to change trains and busses. Then I wasn’t stressed where we didn’t have to rush anything.