The app will work in both Infrastructure with OR without port forwarding and AdHoc mode. In either of the configurations you can still apply a Username and Password that is fully encrypted. Ad Hoc could still use your Designated IP address and User Name and Password.
The app will be able to cater for your specific configuration. If I was at a competition I would probably be doing the same thing with a wireless router just so I could get greater range. People would still have to know the ipaddress that was assigned to the Wifi Guru from your wireless router.