Even back in iOS 5 you could turn off a lot of the built in Apple functionality. I recently turned off the YouTube app because it wasn't working any more. Then just install whatever apps you want your kids to use. You can even turn off Safari and install a more restricted browser like the McGruff browser on the iPad (available in the App Store and works with iOS 4.3 or later) then in Restrictions don't allow download and installation of apps. That should result in a pretty tight iPad.