Not sure I entirely understand the question....but it sounds like you want to enable parental controls, but want to avoid having to password your own account?
I'm not to sure about all the setting/password requirements for user accounts. But based of your question, could you just make another administrator account to set the parental restrictions desired and password that account in order to leave your account without a password?
However, since your account would not have a password, the user you are trying to restrict could log in under your account and change the restrictions (assuming your account is an administrator account as well).
Not sure if that would work, or if someone else out there, that knows more about user account restrictions, has a simpler solution...