Here's an option...
I think you're looking for an iPad management service like PageClean.com
Basically, they act as the filter for content that goes to your iPad. Companies that give their employees tables will usually have their IT department act as the "administrator" for the device, but if you don't have your own IT dept, a service like this will basically do that for you.
It's a different approach than installing an app, because it sits on the actual network layer. So you can still use whatever browser you want (Safari probably) and get the benefit of the filter.
The other biggeest difference is that the filter can be locked in place with a passcode. (and you can have them tell you the passcode.. or not if you don't want them to). It's a completely different part of the iOS api that apps can't usually access, because it's meant for corporations to manage their devices.