As others already posted, waits can sometimes be greater than 20 minutes.
So, he will need to be ready with whatever strategies/techniques he normally uses to deal with his issues..
For the airport, we have used TSA CARES; you can find more info on the TSA website at TSA.gov
It’s important to be aware that what is available at each airport varies and it was made very clear to us that TSA Cares doesn’t shorten the wait. For example, they can’t put you into the PreCheck line unless your boarding passes were issued with PreCheck.
They may be able to help make the wait more tolerable (depending on the airport). We found they were very helpful at our home airport (Minneapolis/St Paul), but not very helpful at Orlando.
For restaurant, avoiding peak times will be helpful, both for counter service and table service. Many counter service restaurants have Mobil Ordering, which allows guests to order and pay for their food on a smart Phone using the My Disney Experience app. When ready, you go to a Mobile Order window to pick up your food with a minimal wait. You will still need to find a table, which may require a wait or looking around if it’s busy.
You might also want to look into a service called Touring Plans - they can help with planning for the park, times and attractions with the shortest waits. It won’t eliminate waits, but will help you to be in the least busy places.