Thanks for the suggestions!

You can remove safari from the ipad so that they can't browse the internet at all. Go to settings -> general -> restrictions, then turn safari off. If our kids want to use the internet they can use the family desktop in the living room as it is much easier to monitor.

You can lock the iPad into an app, so your kid would be able to just play that app and not exit out of it.

After reading the other thread on the child who got into porn on the ipad: Can someone recommend ipad controls or apps to restrict adult content?