PotC is a very difficult ride to get in/out of if you have mobility difficulties. If there's no way to comfortably get him in/out with assistance from family members (CMs cannot help), then you may need to avoid it.
For IASW, he could bring the wheelchair through the queue and use the alternate entrance. He could then use the wheelchair accessible boat (either in his wheelchair or transfering), which would be a bit more straight forward. I will warn you that this is one of the queues where using the wheelchair accessible entrance does often result in a longer wait, especially if he needs to use his wheelchair on the boat.
I would really suggest that he bring the wheelchair through more ride queues. If he wants the walking time he can always push it and then sit when he needs to sit, but some of the ride queues are *very* long (Soarin' is about 1/4 mile and it's not the only one that long). There is no way to cut down the distance walked. It's better to have the wheelchair even when he doesn't need it than to be in a queue and realize after you're 1/2 way through that he can't go any farther. Also, you do so much at WDW that even being pushed in a wheelchair can tire you out far more than it does at home.
For rides with moving walkways, most can be slowed and/or stopped. Peter Pan and TTA are the only rides that cannot be slowed or stopped. Occasionally if you at at Peter Pan for either the first or the last ride of the day, they may be able to slow/stop if there are no other riders. TTA is only accessible by the conveyer belt that cannot be slowed or stopped. Spaceship Earth, Haunted Mansion, Buzz, etc. can all be slowed or stopped as needed.
