Lester,
The shutdown commad is for a single computer shutdown.
What I'm about to write, I have no documentation on nor do I know if it works:
Export your installation package and uncheck the option to create a single .EXE file (you want to edit the INI file).
Edit the SETUP.INI file in your test installation package. In the [STARTUP] section, change the line that ends with REBOOT=ReallySupress to REBOOT=Force
Change the other option of SupressReboot=Y to SupressReboot=N
TEST IT ON A NON-PRODUCTION WORKSTATION. This is my best guess on these switches, but I have no way of knowing if my assumptions are correct. I'm sure someone will correct me if I'm wrong.