Supermarkets, cafe's etc? Well, I'm an adult mum with an ASD, and those are my absolute nightmares too.
Why? Well, this is something I wrote about it a while back on here, if it helps. Our senses are often hypersensitive to things you can't hear or see, which makes the whole environment very, very different for us. Supermarkets and cafe's are designed to appeal to all your senses so you buy things, but that same marketing-overload is what pushes us clean over the proverbial edge:
"Into the supermarket, and into a wall of noise. Announcements, fridges whirring, people chattering, tills beeping. The smells hit me as well - bakery, fish, meat, veg, fruit, new clothing. Smellier than standing in a perfume factory for me. And the sights, too: Everything is stacked high with colours, patterns, flashing lights. Overwhelming...just SO overwhelming.
And there's a cleaning machine somewhere, beeping noisily, leaving reflective lines on the floor that are very scary to cross. Well, they are. Can't explain it better than that.
Then there's the people. Loads of them. And I probably know loads of them, too, since I've lived here for years, but I can't recognise who they are. (our brains often don't work properly for recognising people, their body language, or their tone of voice)
I can't go down the aisle for pasta as there's a flickering light over it, which is like a strobe light for me and makes me feel totally overwhelmed, so that's something I'll have to do without this week."
What to buy? So many choices, and I have no idea which is the right one from all the identical ones. For us, choosing something similar from lots of other similar things can take all the mental effort we have. The sound of a distant alarm from a till is louder than a siren to me. The noise from people talking, the unexpected jostling from people trying to get past, it all adds up to some sort of nightmare scene for us.
It's why children with an ASD often go wild or resort to extreme repetitive behaviours in a supermarket or cafe or shopping mall. Not always, but often.
I find it helps me to be able to plan what I will do so that I know as much as possible about the shop and what will happen in it - so I think a visual chart for a child can help, e.g. pictures of the things you'll need, in the order you'll find them in that shop, so he can help find them with you. Er, unless they've moved them all to a different place (eek!). And knowledge of which aisles you'll go up and down in which order, and picking the quietest time you can.
And get a cake for yourself for afterwards - you'll have earned it!
As for the wee thing, I think he's using it as a science experiment as well as occasionally just not noticing. Others may have wiser words than me right now - brain's a bit non-functional...