I don't understand "iTunes is not downloading". The iTunes app is part of iOS. If you're talking about downloading music, please tell us a whole lot more about what you're doing. For example, are you syncing? Are you using iTunes Match? I cannot imagine ...
Anyway, regarding apps, you can only download one app at a time. So I'm guessing you have many apps in the "Waiting" state. Click each one to get it to "Paused". Then, one by one, click it and get it to "Downloading" then "Installing". Once it completes, click the next and repeat.
Well, you still haven't told us the particulars of what you're doing. But clearly you are asking your iPad to do a lot of downloading at the same time.
- Reset your iPad by holding the on/off and home buttons together for about 10 seconds till the Apple logo appears.
- Sync your iPad using iTunes on your computer. Let iTunes bear the downloading and/or burden for you.
- In the future, when it comes to updating over-the-air, do one thing at a time.