Take the tickets quite literally - go park hopping. We have done all 4 parks in only 3 days. I wouldn't skip one park, they all have something special about them. I didn't think that I was going to love AK but do. Best advice hit parks when they open and do half days (I have personal experience with this and love to do split my days in half between two parks).
My personal opinion would be to hit AK when it opens and be out of the park by 2:00. You can easily do the Kil. Safari, KRR, Flights of Wonder, Tough to be a bug, Dinosaur and Lion King by timing everything just right. Go back to your hotel and rest for at least 2 hours then head out for the rest of the night to Epcot (which is always open late) and stay until Illuminations has ended around 9:30 p.m. Next day go to MK and if you choose go to Epcot again afterwards. Then last day go to MGM and stay and enjoy Fantasmic. If time permits you can go back to Epcot and maybe ride TT or MS at least once. Best thing is to have a list of must do rides for each park and hit that park earliest. As Epcot is open late it is easy to go in and ride your favorite rides from 6-9 at night.