Oh gosh Namechange84 that's taken me right back to when it definitely wasn't polite to say "ok"!
I was friends with someone whose mother was rather a formidable cookery teacher at our school and they lived a sort of "sustainable" lifestyle back in the 70s when "The Good Life" was all the rage. I was invited back to play one day, shown the hens and the veg patch and we played and then I was served (I think) a goats cheese and asparagus home baked quiche for tea accompanied with tomato salad, which, looking back, was probably delicious but at the time was a bit much for me (a nervous nine year old with a dairy intolerance and a hatred of raw tomatoes). I remember being very polite and trying a bit but only being able to swallow a few mouthfuls. Let's just say the mother made her displeasure known at the table and I still remember how ashamed I felt (it was probably worse because she was a teacher).
As an adult, I can understand her pov, that she had gone to the trouble of making pastry etc after a busy day teaching and she was understandably pissed off when it wasn't appreciated. Also, I seem to recall that this little girl didn't have friends back very often and had been talking excitedly the visit for ages, and I had the strong impression that I had let everyone down by being too quiet or not behaving in the way they wanted somehow. ( I was a very unconfident child.)
What was bad though was that the mother was really horrible to me in cookery class from that day on, singling me out for punishments etc, when she had previously been fine. I remember the daughter sympathising with me at break when she found me upset, but at the same time trying to justify her mother's behaviour. (V difficult situation for her but I remember being angry at the unfairness.) Needless to say, that particular friendship didn't last and based on that experience, I've always served my dd's friends "child-friendly" things I know they like and I let them choose and serve themselves. The mother did teach me to make very light pastry though, I'll give her that! 
I do remember one mother of another friend who was welcoming in other ways, asking me very intrusive questions about how often I bathed and changed my underpants, and how often my mother bought me new clothes (we weren't hard up or anything, and I was certainly clean and washed, but I did wear all my older siblings hand me downs which was normal back then). I remember feeling horribly embarrassed at the questions but was too polite to say anything. And this same mother used to make a huge deal of laying out her daughter's clothes (all beautiful and new) on the spare bed every night for the next day, as if to say "look what we have and you don't" 
Finally there was the very strict but beautiful mother of another friend of mine who used to make fabulous roast lunches and she'd sneak chocolate in to the bedroom we were sleeping in that night, and then come back later to say goodnight and then do this little act of faux outrage that she could smell chocolate and say "I hope you aren't eating it under the covers" which made us all laugh.
Ah, happy days (sort of!). Suffice to say, attitudes towards children have changed hugely for the better since the mid-seventies.