There's no special meet & greet for children with disabilities. I'm saying this as a mom of an autistic child whose other child has needed a wheelchair at WDW. You CAN discuss possibly accomodations for attractions for somebody with invisible disabilities at Guest Services (invisible meaning the need is not clear just by looking at the person such as the need for no stairs being obvious with a wheelchair). There are no accomodations for character M&G though except for some Make a Wish children which is significantly different than saying for all children with disabilities.
What do you mean by "what else can you get?"
