As bad as it is to get placed on a gluten-free diet as an adult, I've often thought of how bad it would have been to be diagnosed with celiac disease as a child. It has to be tough to watch all the other kids gorging on glutenous treats at parties, knowing that you can't have them.
I hadn't even given any thought about Halloween. I'm guessing that very few households in the neighborhood know if their trick-or-treat candies contain gluten.
But today I found an excellent article on website celiac.com about Halloween. It has a very thorough list of gluten-free candy, and also candies with gluten that you should avoid. You can read the list here.