I don't speak from a beauty perspective here but a personal one
My nan was a VERY proud lady, she was always immaculately turned out, even if she was only popping down the shops for a loaf of bread!
She struggled more and more as she got older and thankfully was in a nursing home where my younger sister worked and she had a great carer too and so the little things that were important to her carried on - she loved having her nails done, she struggled doing her feet as age took its toll but having nice shapes nails with a clear polish made her feel like standards weren't slipping.
Some of them might be VERY aware of increased hair growth (again thankfully my younger sister was there and made sure nan's was dealt with
) - speak to the supervising GP first for each potential client before carrying out anything but some ladies may in particular want facial hairs removing. Pick a suitable wax and ideally one that you use oil under to minimise potential for damage. But only go ahead after speaking to a GP!
Gentle hand and foot massage I imagine would go down well... If you already work there you have a fair idea of the problems with older skin and how thin it can be, how easy they will bruise and what different medications might do...
