At this point I want to be able list explicit sites that I don’t want them to access, plus list sites by content (i.e., pornograhy) or function (online chating with strangers).

Finally, I’d like to explicitly designate which system preferences my children have access to. For instance, when I choose to restrict access to sensitive system prefferences, the “security” preferrences are still available to my children. They use the security preferrence to reset the “wake from sleep requires a password” control so that at bedtime they put the mac to sleep, and then sneak downstairs after everyone has gone to bed and wake the mac directly into their user.