I think its a good idea. Our youngest has a passcode for her iPhone 4S that is now an iPod. Same thing with the iPad 3. Since she takes them around with her outside of home, its a good security best practice to have a passcode in the event the iPod/iPad is lost, or stolen. Chances of the latter happening in a church setting are probably quite low, but again a good best practice since App store and iCloud information is typically tied to the parent. In other cases older kids may want to help "fix" the iPad, and may have best of intentions, but might end up changing the setup by adding apps, changing configuration, etc.
Edit: Just saw Zerog's response after mine posted. Zerog nailed it. Most often parent's info is tied to the kids devices.