Unless I am totally missing the big picture here this is a pretty standard setup. Splunk recommends to use a agent called universal forwarder to get windows data from remote machines:
http://docs.splunk.com/Documentation/Splunk/latest/Data/ConsiderationsfordecidinghowtomonitorWindowsdata
If the 2 new computers can reach the splunk enterprise installation over the network this should work. Monitoring the event log and the security log is not a problem.
1.) Set up a TCP data input on your splunk enterprise server (where the indexes are, 9997 is the standard port):
>> Documentation: Configure you inputs
>> Documentation: Get data from TCP and UDP ports
2.) Install the forwarder on the 2 computers configure them to send the data to your splunk enterprise:
>> Documentation: Deploy a Windows universal forwarder via the installer GUI
>> Documentation: Install a universal forwarder on a Windows server
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