When I was a kid, late 60s/early 70s, Halloween was a very minor thing. It existed, but only on the day -there was no build-up, no decorations, and definitely no trick or treat. You'd maybe draw pictures of witches at school. Maybe there'd be a spooky story. The real main event of that time of year was Bonfire Night. I don't think I'd ever seen a pumpkin at the time, I knew of them only from stories - like Cinderella.
I first came across trick or treat when staying at my sister's place in the US in the mid 80s. She was out that night but had bought sweets and left me instructions to hand them out, which I ignored. I just sat in the back room of the house drinking beer and eating chocolate.