Well a USB keyboard with a PS2 port on it makes the PS2 mouse just appear as a USB HID mouse, same as a USB mouse... however, I'm not sure that the touchscreen mouse driver appears as a standard HID mouse, so it may or may not work. The software does support multiple touch panels on the different monitors, so I guess, just get some stuff together and try it! They have a free demo.
The more I think about it, the more I want to try getting one of those USB video cards and putting a second monitor up front... I already have the monitor too