We are going to WDW in June, and I am wondering if he is eligable for the guest with disabilities pass?
What you are asking about is a Guest Assistance Card (we abbreviate it here as GAC, to save on typing all that). It used to be called a Guest Assistance
Pass, but they changed the name a few years ago because people thought
a Pass meant they would get instant access to rides without waiting. It is not meant to (and often won't) shorten your wait in line, but it will give you a more appropriate place to wait (like somewhere out of the regular line with less distraction). Someone who has a wheelchair may not not a GAC because most of the lines are accessible and the CMs can see the wheelchair and know what to do. The GAC is a way to let CMs know what sorts of assistance someone needs if they have
invisible disabilities (or more than just needing wheelchair accessible access).
You request the card from Guest Services at any of the parks. Bring your child with you and be prepared to explain what difficulties you need assistance with. Not all GACs have the same wording; they are individualized to what the person's needs are. A doctor note is not necessary, but can be helpful with invisible disabilities. The CMs are not medical people though, so have the doctor keep the note short and in English, not medical terms (I am a nurse, so I am fluent in "Medical", but the CMs are lay people and really won't understand or need to have 2 pages of medical diagnosis - I have seen people who have a big enough file with them to be their entire medical record). GACs are issued for your entire length of stay and the same GAC is valid for all parks. The GAC will usually be issued for the person with a disability plus up to 5 members of their party.
To use the GAC, show it to the first CM that you come to at a ride. You will be asked to use the GAC sparingly - using fastpass if available and just waiting in the line as usual if the line is short or your child is in a really mellow period. We do get a GAC for our DD, but even when we have gone during Easter/Spring break, some days we don't need the GAC at all. Just having it though does help (sort of like insurance - even if you don't use it, it gives you peace of mind to have it).
The CMs at the status board (where they list show times and wait times for each attraction at each park) can be very helpful in knowing when to go to a specific area to avoid a wait. Sometimes the ride that has an hour wait in the early morning is a 5-10 minute wait later in the day. Even if you do use the GAC earlier in the day, the area will be much more over-stimulating and more hectic at the time when the wait is longer.
This website has a lot of helpful information - especially for touring with kids with autism or ADHD.
