"I understand that many don't like to hear this type of thing, but it's important to know where the customs we observe come from and why we observe them."
Well, Jesus was not born on December 25. From what I understand, the whole reason why we celebrate Christmas in December is because early Christians wanted a holiday to counter the pagans' Winter Solstice. Does that mean we shouldn't celebrate Christmas?
I am very much a Christian, and while I try and avoid the occult, I don't see anything wrong with a kid dressing up as Spider Man to get some free candy (Provided the kid is supervised, of course).
That's exactly what it means. The Lord's holy days, the ones he wants us to observe, are listed in Leviticus chapter 23.