Or just, you know, have your kids obey the rules. Without your daily intervention.

Ah, I want to live in this magical fictional world too. (:

I worked at a YMCA with kids for 7 years. As many as 35 at a time by myself.

This is no magical fiction world, I assure you.

Respect them, have reasonable rules, discipline every single rule violation (most important), and have fun. Suddenly you'll find kids are awesome.

Yes, how did parents control console use before OS-level time controls? The problem seems intractable.

On Windows at least, the account locks up similar to a password-protected screensaver, except you can't log back in.

The timer method does work (tried and true), but it's far, FAR easier if the computer automatically locks the account.