I don't think Paleo principles mix well with Halloween, period. So, you either buy the mixed bags of Baby Ruths, Butterfingers, and Crunch bars...or you just turn off the porch light.
Either that, or you can hand out something that gets tossed in the trash.
The longer I'm on Paleo, the more I've come to understand that minute, infrequent exposure to Neolithic foods, processed foods, etc. isn't the problem. It's the prolonged exposure to these things that seem to lead to systemic health conditions. And, I'm also coming to suspect that wheat & fructose are 90% of the problem.
So, if you put a Green & Black 85% chocolate bar in someone's plastic pumpkin full of candy corn, circus peanuts, and Tootsie Rolls is it really going to make a difference? Especially if the parents end up eating it anyway?
Sometimes we have opposing values -- for instance 1) we want to participate in a widely practiced tradition in our communities (like Halloween) and 2) we want to abide by our Paleo principles. Sometimes compromising makes sense, and sometimes it doesn't. This is one of those scenarios where it doesn't, IMO, and it falls under the 'dont-worry-abboudit' category.