My impression is that within the UK there were regional differences, about these 'autumn' festivals, and you can see how they merged into each other. I see 'trick or treat' coming from 'if you don't give us one, we'll take 2, better for us, worse for you' rhyme we used to say when asking for bonfire wood.
We certainly 'celebrated' Halloween and my grandmother told of things like peeling an apple to see if the peel made the initial of your true love, and various rituals involving mirrors.
I told my kids they were rituals from old times about coping with the coming winter darkness. And if you look across the northern hemisphere, most cultures have something: from Diwali to St. Martins' Day. I lived in a large town at one point, where, to accommodate all cultures, we had, on the nearest Saturday, a 'lantern procession' (there were workshops to make and decorate the lanterns) followed by a bonfire (no guy) and fireworks. My friend who hated Halloween and Guy Fawkes Night joined in happily.