I'm also a big planner but since you have the time I agree with maybe having an open day and see how things go. Or you can let your kids decide!
Here are my thoughts on it if you would rather plan ahead of time: I think that with the ages of your kids you could easily spend 3 days in MK, even with Toon Town closed. In fact, that actually sounds nice since you could take it a bit slower. If your touring plan includes both Dumbo & the Rapunzel meet & greet, it's definitely helpful to divide those up so that you can hit them first on two different days. Also, not sure if you are planning for the night shows but if you did a 3rd day at MK you could plan on doing it back to back and sleep in the 3rd day there. My daughter LOVES Dumbo and the character meets, both of which can take a bit of time for us. We also love the Move It Shake It Celebrate It Street Party and we often see it at least twice.
On the other hand, the benefit of having 2 days at AK is that it would be easier to plan around the shows. You could also think of it in terms of which attractions at either park do you feel that you and your family would be interested in enjoying more than once (or twice!).
Have fun whatever you decide, I'm sure you will have a great trip