I would rather not use the app for this, one of the reason being that it does not sync real time and the second being that you are far too limited with regards to the fields you can capture.
IMHO, the best approach is to created a non tracked Marketo landing page with form.
1 of 1 people found this helpful
+ 1 for Greg's recommendation. Using a non-trackable landing page would be a better option, rather than relying on the event check-in app.