I think what you have here are a couple of older folks who may be unfamiliar with what "streaming" actually is.

When I was installing, I'd often run across people who thought Sonos had a monthly fee.  Older folks tend to be against monthly fees.

I assume they have an iphone/tablet?

Personally, I think you're doing them a dis-service by not at least letting them test drive one for a week.  Take your pick Sonos Play 1 or Heos unit.  Stop by, connect it, show them how to use it, and let them play with it for a week.

At the end of the week, if they want to go back to the stone age, take them.

For the record, I installed exactly 2 Russound units and 2 Nuvo Grand Concerto units.  The Russound units are still working (although the only 2 sources are now sonos Connects).  The Grand Concertos both died and Nuvo no longer carried the streaming unit (MPS4).  Same customer, 2 different homes.  They  got replaced by 30 sonos connect amps.