When your event is in production you don't need to worry if the volunteers will remember the shifts they've been assigned, CrewPlan will send out email reminders 24 hours before to each volunteer, reminding them of the upcoming shift. You also have the option to send a text/sms to each volunteer assigned to a shift, all you have to do is enable this when setting up the shiftplan.
You can merge data from the shift so each message will be individual. In the example above the message would be like this:
Every user has the option to subscribe to a calendar with all the shifts they are assigned to, this makes it easy for volunteers to have assigned shifts added to their calendar on smartphones/tablets.