Hi!
Let me start out by saying that my oldest is 5yrs. old and wears bilateral hearing aids. WDW does offer assistive litening devices and sign language at some shows if you plan ahead. I'm not sure if your child signs or not. However, in our case, our son does not. He has children in his class with hearing aids as well as cochlear implants. His teacher focuses on cued speech and lip reading. Therefore, sign language is not helpful to him, and the assistive listening devices aren't helpful with the type of hearing aids he uses.
SO, these are some things that WDW did for him (and we are so grateful) on our last trip.
We brought a letter from his school explaining his type of hearing loss and special needs. We took it to guest services and they gave us a card so that he could have preferential seating at shows (and even on rides where it was important for him to be seating closest to a sound source). Speech becomes unclear to him farther than 6 ft. from a sound source.
I dont know how new your childs cochlear implant is (or how used to it he/she is) but hopefully you and your family will find the above tip somewhat useful.
Have a truly WONDERFUL trip!