|Net Nanny or similar is easiest for Internet. Just block everything and allow sites YOU choose.|
Monitoring software is sneakiest, but somewhat costly. Antivirus applications need to be set to work with this. You can watch the screen in real time from remote locations.
Spy cams are easy to find and set up. But at this point, removal of the PC from private location to public location is better choice. Everyone re-arranges furniture or rooms.
Advise: Think through your choice... it can cause more issues / problems than expected.