As the program coordinator -- and therefore a faculty member -- we suggest that you:
Do not send the message out to your program faculty. Instead, let your AD know that it is struck work, and asking faculty to do this work would be analogous to asking them to cross a picket line.
If you are directed (not "expected") to send the message by your AD:
Send the message, with a preface that you've been directed to do so by the AD. Remind your program faculty that the work being asked is struck work, and doing this work would be analogous to crossing a picket line. Contact the union immediately.