In reply to VS4b:
Think you do this house wide with OpenDNS.
Basically you configure your router to use DNS servers that aren't your ISPs which has other benefits. I'm sure you can implement webfiltering with it as well. I set up mine years ago.
It also allows you to easily see what wed addresses have been looked up.
THough this will all your devices (not just your Ipad), and wont stop anything on 3g cell connections.
http://www.opendns.com/
Si