My tradition for Halloween is to get each child a Halloween card and mail it to them. They all love getting mail with their names on it. I purchase adorable cards in the dollar store at 2 for a buck. I write a small personal note to each one and place a Halloween sticker on the back over the seal.
I do get to see them all on Halloween when they come to my house for their treat. All of the cousins trick or treat together with their parents and we usually meet as a family at the end of the night.