MK and a "family choice" do over park that you decide while you're there. After going to each of the parks, your family might want to redo one more than another, or maybe there was one day that gets rained out that you want to redo,
Right now HS is barely 1 day. AK is 1 day. Epcot and MK are 2-3 days each. Epcot has the 3 tier 1 fastpasses that we want, so doing at least 2 days there helps! (Test Track and Frozen rides tend to stay high all day/night, Soarin' can go down to reasonable levels in the evening!)
Definitely get a park hopper. I would do 2 days at MK, AK, and DHS. And only schedule 1 day at Epcot. Since your kids are 21,23 and 23 they may want to hop over to Epcot in the evenings to try different food/drinks in the different countries.
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