Has anyone...?

[Mom2Joce]

Upgraded a child using an adult ticket to an annual pass?

 

[MateasMom]

LOL. You know what. That's exactly what I was thinking when I read your other post. APs are one size fits all. I can't see why they wouldn't let you apply the adult pass to the AP, especially considering the one size fits all-ness of the APs. I would call Disney to be sure, but I can't imagine it would be a problem.