Get to MK b4 opening! Very important!
Go 1st to Fantasyland & grab a FP for PP. Ride Dumbo, Carrousel & Snow White. If FP is not ready, go to Philharmagic. If FP is ready, grab FP for Pooh & then ride PP & watch Philharmagic. Then if FP is not ready, ride Tea Cups. If FP is ready, ride Pooh then Tea Cups. You can also re-ride faves if you are waiting for a FP time.
Head to Tommorrowland & grab FP for Buzz. Ride Speedway, Astro Orbiter & if you need to kill time b4 Buzz, ride TTA. Then ride Buzz when FP is ready.
Head to Toontown for Barnstormer. Check out Mickey & Minnie's houses & splash at Donald's Boat.
Take train to Frontierland. Grab FP for SM or BTMRR if you think DS would like either.
Then go to Adventureland while waiting for FP. Ride Aladdin & PotC (if you think DS would like it). If you need to kill time for Adventureland FP, try Jungle Cruise, Tiki Room or Swiss Family Treehouse (whichever you think DS would prefer).
Then go to Frontierland for whichever ride you had FP for. You can now either leave or if you have your heart set on riding both Mountains, wait in line for the one you did not have a FP for. (Make sure you get the FP for the one that had the longest wait)
Then go to Liberty Square for HM (if you think DS would like it). Do the riverboat if you need a rest.
Fit in the parade if you want, or try to ride the long wait lines (maybe the Mountain rides) during the parade.
Fit in lunch somewhere too! You'll finish back at Fantasyland in case DS wants one more shot at his favorite rides!
Hope this helps!
It is a lot to do in one day, but if you use FP & go on some of the "rest" rides you should be ok.
If you plan to spend the ENTIRE day, have a sit down late lunch (after 2pm) for a nice break. Then you'll be refreshed for the evening activities like Spectro & Wishes. Then you can add other rides that I did not mention.