The Shotgun Scan app lets you scan tickets without internet access. All you have to do is download all the tickets on a scan during the last possible internet connection. If you have multiple scans, you don't need to do this on all of them. The one on which you downloaded the tickets becomes the master scan, you can then connect them all by Bluetooth to create a local network.
If necessary, during your event, you can walk away with the master scan to an internet connection to do an update.
Keep in mind that it is important to download everything on a single "master" scan which will communicate with the others. Thus a ticket can never be scanned twice by two different scans.
If you need to use this feature, don't hesitate to check with your Account Manager a few days before the event.