Volunteer Coordinator

Before the convention:

Assist with recruiting volunteers, make a schedule, slot volunteers into it.

Ensure the volunteer training day happens -- the coordinator doesn't have to run the day, or be the person who presents the presentation at the day; they just have to ensure it happens and the volunteers are given every opportunity to turn up.

At the convention:

Ensure volunteers are covering their shifts. In the event of a no-show, find a replacement volunteer, or fill the spot yourself.

Ensure volunteers are getting what they need. There's no particular thing that they need, so this probably just means ensuring they have your contact details so they can contact you if needed.