Just because Moodle for Mobile is not enabled does not mean that they cannot access Moodle from a mobile device. It just means that they won't have a Mobile friendly interface...they will have the regular browser experience.
Though, if you are on 2.8 or later, the themes are builtin to be mobile friendly anyway.
The attendance plugin is installed on the Moodle server, not on a mobile device. Your TA's will be able to access through any browser on any device.