We've done three parks (everything but AK) several times. One of the times we went to Epcot three times and enjoyed two sit-down meals! Questions:
Is it an EMH day? If so, are you staying on-site?
Are you willing to do the single rider line at Test Track?
What are the park hours that day?
Without the answers to the questions and assuming no early entry, I would:
Start at MK. Be there before opening. You'll have no wait for the first ride and some for the second.
Monorail to Epcot. Get a Fast Pass for Test Track and wait in line for Mission Space. If it is hours before the Fast Pass, head on over to MGM. Get a Fast Pass for one and wait in line for the other. Remember to return to Epcot in time to use the Fast Pass -- probably not until evening.
Then get a bus to AK. We have found that there are usually no lines late afternoon, so I don't see a problem getting on those two. Check at the little information booth to decide which to do first.
Then you have the evening to go back to whichever park you want or perhaps to get to Epcot for Test Track.
Now, if it turns out that there's EMH or better-yet E-night, you can add another dozen rides to your plan!