Actually, Lisa, kids with Down's syndrome suffer from an inordinate variety of medical problems that can reduce the number of things they can enjoy at theme parks.
Heart problems, hypothyroidism and vertabrae instability are just a few of the problems these kids and adults can face.
Nonetheless, there are so many things DS children and adults as well as otherabled folks CAN enjoy at WDW that I do understand their policy. Our son with DS loves WDW and gets more than our money's worth out of his AP.