Volunteers Adding notes to shift signups

We have an opportunity for volunteers to provide dinner and the menu is their choice. At the moment, there is no way for the volunteer to input what they are going to provide after signing up, forcing them to remember to email us (which hardly ever happens). We then have to chase after the volunteer for the dinner menu and often don't get it in a timely manner. Volunteers have told me that the lack of ease is a deterrent for them signing up.