As I mentioned a few weeks ago, My Disney Experience, the Shop Disney Parks App, and even the Disneyland App (per the comments to my original post), all crash at launch on the iOS 11 Beta (currently, in developer beta 4 and public beta 3.) I’ve submitted bug reports using Apple’s beta feedback system (and been contacted to test a fix or two), but the crash is still occuring.
If you’re planning a trip to Disney World in the near future, and you want to use MDE for things like refreshing Fastpass+ selections, I would recommend not installing any iOS 11 beta. There is always a chance that the next iOS beta will fix things, but I think it’s possible that the fix for this crash requires Disney to submit a new version of its apps that is compiled against the iOS 11 SDK. That would mean no fix would come before iOS 11 is actually released (which has, historically, been in mid-to-late September.)
You have been warned!