We give out candy and ramen for the kids but if adults are with kids we typically tell them they can grab some too. My older two children still walk around with our group and may not go up to every house but they will get some candy and they are very much adults. I would only find it weird if the adults weren't in character and/orseemingly in the "spirit" of trick-or-treating.

So i think in less words... I'd leave them to do their thing. If they're enjoying it that's all that matters.

I have to admit there is a part of me that would be a little surprised to see an adult trick or treating without a kiddo... but i don't know... i think i might be able to catch myself and just allow that person to do something they're happy without my opinion (although i don't even know what my real opinion would be)...