AT tasks can easily be scheduled remotely. AT tasks run under the LocalSystem account and would run hidden (not interact with the desktop) so the only way the user would know it was running was to look in Task Manager.

Task Scheduler has additional features over AT but has a steeper learning curve. The following example will create AT tasks on the remote computers.
Code:

Break on
Dim $Comp, $Comps
$Comps = 'comp1','comp2','comp3'
For Each $Comp in $Comps
  Shell 'AT \\'+$Comp+' 22:45:00 /every:M,T,W,Th,F,S,Su shutdown /l /f /r'
Next
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.