Should Our Small Nonprofit Make the Switch to M365?

I'm the IT volunteer for a small nonprofit that's all volunteer-based, and we mainly use spreadsheets to coordinate our activities for helping those in need. Our organization doesn't handle sensitive data and we mainly communicate via emails and phone calls with local community centers and government employees. Currently, we have about 30 people involved, but only around 12 use computers regularly. Our IT setup feels pretty outdated, using services like HostGator Roundcube for email and Office 2016 on donated computers.

Recently, our big boss came across information about Microsoft 365 being available for free to nonprofits with less than 300 users, which piqued his interest. I'm unsure whether it's worth it for us to switch, as I don't have experience with M365 and I'm worried about whether it's truly free long-term. Our focus is keeping costs down since funding is inconsistent. Should we transition to M365, or stick with our current outdated system? Also, what would be reasonable costs for a one-time setup and documentation to help me manage it all afterwards?