The app store has been experiencing outings.
If there are multiple apps trying to download at once, only one can download at a time and the rest say "Waiting" until it is then their turn. Try this. Double tap the icon of the Waiting app, and it should resume the download.
Another thing to try - Turn the iPad Off & then back ON.
If that doesn't work:
• Log out of your iTunes store account. Go to Settings > Store > Sign Out Then press the Home button.
• Then press and hold the Home and Sleep buttons simultaneously and don't release them when it brings up the Turn Off screen; keep holding them until the Apple logo appears.
• After restart, the Waiting should be gone.