Could you do the hair as gray/bald in middle/glasses/cardigan.
It's hard to do an icon without being sterotypical of something
Women's toilet - skirt
Conductor - uniform
Policeman - bobby hat/truncheon
Business man - tie
Business woman - skirt cravat
Disabled - wheelchair (which I hate because you don't need to be in a wheelchair to be disabled)
Sikh - Turban (I don't know if that's offensive, sorry if it is)
Bellhop - hat
I'd go for something that's a common denominator (you could call it a stereotype I suppose), something simple like glasses and a 'dated hairstyle' like below.
It's clearly an elderly couple but I wouldn't say it's a negative portrayal of them. I'd just focus on the faces/hairstyles. Just a few faint lines beside the eyes could be enough to convey age (and wrinkles are something you can't really avoid).
Thanks for the replies. The context is a health sector infographic for a government department. I'm quite limited in what I can achieve as it's a replacement icon for part of a set comprising very basic/reduced figures so small details are problematic.