You'll want to take a look at the guides for guests with disabilities before you leave. You can find a link to them on the disabilities board. You can also pick up copies of these great guides at guest relations in any of the parks, although some seem to be better stocked than others. The guides will tell you which shows have interpreters available and give you some other basic info. When there are no interpreters, many attractions/movies/shows offer captioning devices. Depending on how well your 6 y.o. reads, this may be an option. Finally, be sure to point out to your son that many cast members can sign. Just look for a pin with a signing hand on the CM's name tag.