All LANs, above all really big ones, must have a supervisor who administers, manages and controls all the functions of that LAN and the machines connected to it.
If, at this level, you still don`t have any program and, to start with, don`t want anything complicated, what you need is Host Administrator. It is a very basic and simple program, totally free, that needs no installing. From Host Administrator you can administer the information of each TCP/IP host for each machine.
For each IP address Host Administrator gives you the name of the machine and even lets you add or edit additional information, like the username of the person who controls it.