From my understanding, unions require a vote from employees before being able to negotiate contracts with management. So if they want a few more people to come to a meeting, it’s probably because they need a sense of whether they’re gonna win that election and / or there is interest from more than a single employee.
Getting a union can be a long process, just to get to the bargaining table. Successful campaigns require a tireless dedication from at least one employee who wants to fight.
All worth it IMHO, and I’m heartened to hear about labor action for EMS staff. Best of luck in your efforts!
Same - I used this tool which worked great for that workflow:
http://www.traynier.com/software/steammover