You need to talk to your kids. There is nothing you can do if you believe that your children will do whatever they can to sidestep your efforts for controlling their access.
If you locked down my Vista machine, I would simply boot from a LiveCD Linux distro and surf the net for whatever porn I could find.
Now, you need to realize that it is not illegal for one of your neighbors to operate an open (unsecured) access point. However, it is illegal for you to try to connect to their router and attempt to gain information about them. (PPOE, email address, etc.)
If you are really worried about you neighbors open AP, install
NetStumbler on your laptop and talk a walk around your neighborhood. Based upon signal strength, you will easily be able to tell where the open APs are located. Then, you can politely approach your neighbors and have a conversation about helping them secure their network.