That /silent switch works.
Here's what ended up working the best for me:
psexec \\client1 -c -f -i -n 15 -s "d:\downloads\mc\mediacenter13.exe" /Silent
psexec \\client2 -c -f -i -n 15 -s "d:\downloads\mc\mediacenter13.exe" /Silent
I set that up as a batch file.
Now, I download the latest MC build, change the name so it gets saved as mediacenter13.exe in the path referenced above.
Then if I feel the need to update the client computers, I kick off the batch file.
If a computer is offline, it will attempt for 15 seconds, and then skip it.
psexec is a power tool available from Microsoft. Google it to find a download source.
psshutdown is also a cool util that allows you to sit at one computer and schedule reboots of other computers.
I use that one at work all the time.