I didn't vote because I'm not sure what we're doing.
I am going to try to find a Halloween themed t-shirt for myself. Hopefully they will be in stores in early Sept. I have Halloween sweatshirts, but I need a t-shirt for WDW.
I want the kids to be comfortable, so I am leaning toward getting them Halloween t-shirts, too. If I can find costumes that are easy to pack, not too heavy to wear in hot weather, and comfortable to wear on rides, then they might do costumes. Otherwise, they will be sporting Halloween t-shirts.