Jimmy asked the right question. You have to buy applications for the disabled hunter category. Yeah, it's stupid, isn't it? All the disabled permits are for antlerless animals, they should be in the antlerless category. Same with most of the youth permits. They only have the separate categories so people can buy applications in mutlitple categories (and therefore spend more money).
Since you already have the regular antlerless applications, you might as well just put him in for some of those hunts, and then buy the disabled applications if you also want to apply for those. It will give him better odds of drawing a permit.
Unless you don't want to spend the extra money. In that case, just go to a license dealer and get a refund for the ones you bought, and then buy the correct ones.