Well, you are right that most SUVs today are really crossovers, with little to no off-road capability, but they are fairly popular, while minivans have been going out of favor. Still, minivans do exist and Toyota, Honda and Chrysler still compete in the category; GM never really did, unlike in the SUV and Crossover markets where they have been very competitive.
Putting aside the original nitpick, I do wonder why Disney did not actually use a minivan (probably the financial incentive to use GM was too great) since it would have have provided their fleet with better mileage, the vans would have had better access to the 3rd row and likely more legroom, and there would still have been more room for car seats, strollers, and any things a family might need.