Home Network

Dear Friends,
help needed once more and thanks in advance for those who will,
I have a small home network with 4 PCs connected wirely to a wireless router (with 4 cable plugins, everything is working just great and I do have a very good connection on all PCs, the issue is that I want to control my kids access to the internet through one specified PC and let them do that only when I give them the permission to, meanwhile I need to keep that PC connected on the home network all the time, please help me.