I've noticed this too - and am most impressed that Pianeer took the trouble to think about what the audience would enjoy.
I think "short light" classical would be enjoyed, if mixed with other fare.
Don't forget that an old people's home could easily span a generation in tastes - but perhaps the younger oldies are more mobile and likely to come to a concert than the oldest oldies?? Today's 97 year old was at high school at the height of the Roaring Twenties, but today's 77 year old and his or her older and younger brothers and sisters were schoolkids and young adults during the war.
My parents, if they were alive now, would enjoy hearing
* hymns no longer included in the modern hymnals
* anything from the "classic" musicals and shows they went to see when dating.
* Gilbert & Sullivan, which was standard amateur performance fare in their young days
* some of the more staid early pops such as Peter Paul & Mary
* Repertoire from people like Nana Mouskouri and Julie Andrews
* themes from 50s and 60s movies and TV shows, although TV was much less part of their lives than for people born postwar.
Assuming that there will be a fair proprortion of hearing-aids (and hearing-aid refuseniks

), ideally it would be great to know whether instruments like violin or high passages on flute are going to be uncomfortable to hear.
You could try asking the home staff if they think residents would enjoy chatting about their favorite old music - if you *do* have some old wartime books, musicals, or singalong books (often found in junk shops!), a glance through might jog some enjoyable memories, even if you only actually play one or two pieces.
Musicals: (* biggies for the 70-plus UK generation))
Oklahoma
*South Pacific
*My Fair Lady
West Side Story
A Funny Thing Happened on the Way to the Forum
Oliver
Salad Days
Camelot - forogtten now, but popular in UK and the farflung cropstones of the empire
Funny Girl
*Fiddler on the Roof