Do your kids like to use the computer? Do they have a time limit? How do you moniter what sites they go to?
My kids like the computer and we usually give them a half hour at a time to play games online. They each have their own favorites file and I am always walking by to make sure I know where they are. The computer is in our living room and I have to walk right by it to get to the next room. As the desk is located next a half wall, they have no online privacy.