iOS 7.1
/Apple recently released iOS 7.1 which refines the iOS 7 experience, and sorts some issues, including AirPlay dropping out. Read more about the update here: http://www.apple.com/au/ios/ios7-update/
If you are using Apple Configurator, you can easily update your iPads in the 'Supervise' section, by selecting the iPads you wish to update and changing the 'Update iOS' pop-up menu to 'When Update is Available' and clicking 'Apply' down the bottom of the window.