As PP said-it really is a matter of personal preference. If at all possible, I would try to move your ??? day to the end of your trip so the crew can decide where they would like to go. Perhaps you can try for the FPs of concern earlier- someone with more experience than me will have to assess your chances. We don't get to WDW often, so my boys like to focus on what they want to do, not following a plan. (We use hoppers so they go wherever whenever.... it must be very difficult to feel like you have to lock in each park day ahead of time....I am sure you are not alone in feeling stressed.)
For what it is worth, I would probably choose AK. Boys love EE, the Safari is great and there is just so much to linger and enjoy (animal trails, performers...). FWIW, my kids do like multiple visits to HS for ToT and RnR....they have never been into Epcot attractions aside from TT and maybe Soarin'....they just don't appreciate the World Showcase as much as my husband and I do.
ETA I was also thinking that more AK time would allow for an awesome extra experience like Caring for Giants or the rhino tour.
Are you doing the fantasmic package at mama Melrose strictly for the Fantasmic seating benefit? If so, I would keep in mind that there are other strategies for Fantasmic seating...you may not want that alone to decide for you.
Just know that, no matter how much you know or plan, you can't do everything and that is ok. It will still be magical!!!