I just wanted to add that enabling offline is not a requirement for using the mobile app. It is possible to use your application online-only. You only need to enable offline if you wish for your application to work without a reliable network connection. Offline support does however require a mobile application. If your mobile application will always be used where there is a reliable network connection, you may opt to not enable offline.
You can use the existing application as is as long as you're HTML 5 compliant. The screens are responsive and adjust themselves on different form factors. It is *not* required to enable 'offline support' to get the mobile app working.