Hmm, I'll check for sure tomorrow, but I'm fairly sure that you can't sell at someone else's Re-Tail. I have two towns and frequently sell things in my other town's Re-Tail. The option to ask about selling items isn't present in the menu options when talking to Reese with an out-of-town character. Of course they can still sell the usual things, andbuy any items for sale, but I had thought they couldn't sell anything because the option to find out how is missing.
I guess if that's the case, you could get around it by having people give the item to you (drop it outside) and tell you what price to set it for. Just an idea I had, I don't know how well that would fit your plan.
I would like to vote for the Re-Tail Game, but I'll wait til I've checked my games tomorrow.
It's a very generous thing you're offering to do for people here.