Old Navy is running a sale right now. The sale runs through 9/25 and there doesn’t seem to be many specifics about any exclusions other than gift cards. You can see the commercial they have running about this sale here.
I think this might be a way to get a nice deal on Halloween costumes. The costumes are about $25- so about $31.00 for 2 costumes!
They are also offering a 30% off Old Navy coupon for in store shopping through 9/22 only.
Usually I have found you can’t stack these types of deals but I think it is certainly worth a shot if you are headed in.