[Edi]

Four people on one computer makes for a very crowded, frustrating ame very fast when you're switching chairs every 30 seconds.

Two copies with two people per computer each is quite doable. You just need to select two players as human from the game setup on both machines (the "Me" setting) and then divide them up as you please.

One computer will be running two instances of CoE3 (one instance of server, the other as client).