only -yes, I do my best to not assume anything, and I don't ask impertinent questions! :)
I remember being out with DH and DD last year at a country show. There were some 'vintage' (as in 1950's) cars on display. DD was looking at them as were an older man and woman. As we passed each other we smiled and said hello. DD told them she liked the cars. The woman looked at me and said, "Oh, I expect this car is older than your grandma."
I said "No, I don't think so. Her grandma was born in 1942"
Woman then got embarrassed and went, "Oh. I mean - er, I didn't, um...." and then she wandered off.
Not as bad as charity shop woman from a few years ago.
DD: "Hello"
CSW: "Hello Darling, what's your name"
DD tells her.
CSW: "It's nice that your nanna has brought you shopping."
Me: "I'm her mother, actually."
CSW: "Oh. Are you sure?"
Me: "Er...yes!"
CSW: "Only you know, it's hard to tell, people have children at all ages."
At this point I decided to leave the shop before I ended up giving her a mouthful.
Yes, it is hard to tell. Yes, people do have children at all ages. No, it makes no difference to you whether the child is shopping with her mother, grandmother, great-grandmother or sister. If you want to make small talk then let's talk about what you're selling, what the weather's doing, how nice my shoes are, how well the hairdresser did your hair...