You are not likely to find any accurate information on average age. Disney won't even publish an accurate attendance let alone anything as specific as age.
If your company is looking to partner with Disney I would think you have some VERY high powered executives and attorneys working with Disney's executives. Surely they would be able to ask that question, though they aren't likely to get an accurate answer either.
If your CEO doesn't understand Disney's ways, I would be quite surprised if they land a partnership. Let us know what happens.