Why not use a scheduled task on the local computer? Easier and more powerful if you use a Domain Account that has local admin rights.
Run the Scheduled Task with an account from the Domain that you control that is a member of a Global Group that is added to ALL workstations. Members of that control group can then have Admin rights on all local workstation computers.
Then from there you can do a couple things. Have the task simply shut down the computer when you want or you can have it run multiple times or at specific times where it reaches out to a shared directory from a server that you control rights on and it reads and looks for it's name and if found it shuts down. The you can add the names of any computers you want to to a control file and have it either shutdown or restart, sort of on a delayed demand