To set all your apps on your iPad to automatically update, go into the iPad's "Settings", scroll down and tap on "iTunes and App Store".
From here, choose "Automatic Downloads" near the bottom.
To turn on automatic app updates, tap in the white oval next to 'Updates', swipe until green appears. The apps will now update automatically. Apple will even ask you how often you would like the apps to update and whether you would like it to update only when you’re on Wi-fi or also if you're on a cellular network.
If you have automatic app updates turned on and would like to check which apps updated:
1. From the App Store, choose "Updates" Here you can check when apps last updated.
2. From the Notification Center in the “All” tab, check which apps were automatically updated.