Generally, you should be able to request a quieter room location. This will tend to be one that is further away from everything, like a room at the far end of the hallway on the upper floor.
Of course there is no guarantee at any hotel that you will have quiet neighbors, no matter where your room is located. There is also the possibility of something like the fan (room's air system) bothering him.
Has he tried a white noise machine? That might help.
All that said, CB seems like a good choice to me. Fort Wilderness has a secluded feel, but I think there you could also have rowdy neighbors. If, at some point, your budget allows, the treehouses at SSR are pretty unique. (though they tend to be $$$.)
For the most part, we've had pretty good luck at WDW hotels. I can only think of a few times we had bothersome noise, and mostly that was due to loud neighbors. If your room is near water taxis, you can hear the horns. Near MK, you can faintly hear MK noises, like the train. They are not constant, but periodic. One of few that has, IMO, irritating noise, is the lower floor rooms at teh Contemporary if you get placed near Chef Mickey's.
Sometimes with pool view rooms near the pool, you can hear some pool noise, but the pools now close at night.
For us personally, we are on the go all day at WDW. A full day of exercise = we have an easy time falling asleep, and it is usually a deep sleep.
The hotel quiet pools are often very quiet. Sometimes you might get a loud family, but often they are empty. The one at the Boardwalk hotel was especially pretty with gardens. If you aren't staying there, you can't swim, but you can visit.
Epcot has a few somewhat quiet spots with gardens. The maze garden is pretty quiet. Japan area has a somewhat quiet outdoor seating area with tables for dining and has a water garden. Multiple countries have little museums that are relatively quiet: Norway, Morocco, Japan all come to mind. Most people walk past and don't realize they are even there. The parks tend to be somewhat quieter late at night.
A little more pricey, but he might enjoy club level at Coronado's Gran Destino. The lounge gets busy for breakfast, and around 5pm, but at 6:30am and mid-day it is pretty quiet. The view is lovely, and he can get most of his food there. If the lounge is too busy for him, he can easily take his food to the room to eat. (short walk). Actually, all of you can get breakfast there, plus snacks, drinks, appetizers and desserts. It isn't enough to cover all your food needs, but maybe 1/2-3/4 of it. The hotel has LOTS of quiet pathways, a lake, hammocks (I think they still have them). The lounge is beautiful, a relaxing blue decor.