I think it depends on your kids and their expectations.
Although MK is not our favorite park, it is the park that announces we are at Disney. If it were my family, we'd head to MK on Monday morning - first thing! We'd spend maybe two hours there, beeline to Dumbo with a five year old, get a few other Fantasyland attractions in before the crowds. Then we'd hop - probably not to AK, that park closes fairly early - though the trails can be a great and relatively crowd free way to spend an afternoon - probably we'd hop to Epcot or MGM. Have lunch - either on our way out, or at the new park after the hop. Enjoy that park for a few hours, maybe head back to the hotel for a swim about 2 or 3 before getting dinner and seeing fireworks.
We are big hoppers in case you can't tell.