Help with 3-day plans in one park

We don't have any pre-made 3-day plans but will give you some advice for adjusting your plans. In three days you will be able to see everything you want at the Magic Kingdom as well as re-ride many of your favorites. What might work best is trying to see much of what you want on the first 2 days and using the third to catch up on the few things you missed and re-ride things. Obviously, that makes planning the third day in advance a little tricky because you may not know ahead of time what you will want to re-ride. 

In general, I would suggest splitting the park geographically, which will minimize walking and broadly split up the major attractions. Over two days you could do Fantasyland, Liberty Square, and Frontierland in one day (as we have in our plans) and Adventureland and Tomorrowland the other or you can split it east and west, doing Tomorrowland and Fantasyland together and the other 3 the second day. For splitting evenly over 3 days I would say Fantasyland one day, Tomorrowland and Adventureland on one, and Liberty Square and Frontierland the third although that plan would have quite a lot of free time without re-rides.

It will take a little trial and error when moving attractions to different days and seeing what works out best for you.