Any chance you guys could install the Tapatalk plugin for your forum? Using your forum on a moble device is ok, but still awkward, Tapatalk is a multiplatform mobile app which tons of sites use to allow users easier integration with their forum. It does not require any changes to your system, or the way users login to your forum. It only requires that you install their plugin.
They offer a plugin for Invision Power board (the software your forum uses) here https://tapatalk.com/activate_tapatalk.php?plugin=ipb