MK - if you are standing in front of PoC, to the left of the queue lines there are benches WAAAAY in the back (backs up to a character entrance, I believe). DH naps there frequently. It's nice and cool back there and very shady.
Epcot - he discovered a bench just off the exit of Spaceship Earth (literally, you walk down the ramp, take a left just out of the turnstile thingee). He will nap while riding SE also.
I may have to share some of these others with him......