dear @wwwiebe, it is so beautiful that you keep these traditions (even if modern) with your child, and I think he is not spoiled for this reason! in Italy there is the custom of dressing up as ghosts or witches (but it is not much followed), and it is usually children who do trunks or treats in shops. I think that halloween is a way to exorcise the thought of death and to accept the existence of spirits: if this party is celebrated well it can be good and meaningful for children :-))
continue and congratulations on your curie evaluation