I think without a dedicated category for the listings it would help clarify (albeit informally) the listed item was for charity for the benefit of both seller and buyer.
I hadn't really considered the wording - I was just thinking/typing out loud last night
It's only a thought and as Babs has pointed out your nifty template makes it pretty obvious where the proceeds should be heading. I guess most people will be using the template so it's probably an unecessary hoop for everyone to jump through.