Mike,
I've done similar things several times. Moodle 2's backup is very granular so as an admin or manager role you just go into the course and click Backup and then deselect everything except users. I needed to create two new student user accounts which were left off the production moodle. I created a dummy course on my sandbox server, added the two student users manually, then did a backup with just those users. In the main course on production I did a restore then added to the course and viola les etudienes (students) appeared comme ca! Brilliant!