Respectfully, I'm a little confused. Why does it bother you that she isn't especially interested in the MK? She's not saying they have no interests the "the parks", right? They're going to be staying at WL for 10 days, seem to be planning to visit all the parks (although maybe not HS?), and have FP+s for the rides they really want to ride. Maybe when they actually get there, they'll find the MK more interesting than they remember. If they don't particularly care about that park, perhaps think it's more "for kids" than the other parks, well, that's just their opinion. The "new expansion" of MK didn't do much for me (seems very geared toward children) and I feel like it's taking forever to get the one thing that interests me -- the Mine coaster -- open. In fact, I sort of dislike what they've done, so I'd have shrugged about that as well.
Maybe their vacation plan is to sleep late, stroll through the parks at their own pace, eat nice leisurely meals, play putt-putt golf, swim and sunbathe, check out the other resorts, and go dancing until 2 a.m.