Ask the user....use it as a learning experience built into the tutorial.
Thanks for the suggestion KMT
I've implemented a quick fix using the event UIEventSubtypeMotionShake which is still published in the responder chain for users that have disabled "shake to undo". An event handler manually triggers an undo which lets these users finish the tutorial.
Not an ideal solution as it potentially confuses these users as to when and where their choice to disable shake to undo applies