Switching to Microsoft 365 ecosystem

Im currently part of a volunteer organization, and we are looking to consolidate a few of our different communication and file-hosting channels. We have roughly 100  members, we don't need/ want to get accounts for each member as that would quickly get expensive. We need to consolidate a listserv, and file server ( under 50 GB), and host 2 or 3 different emails. The question is would a single business account work for this? Make a 365 Group and SharePoint site for the organization and add each member as a guest. All we want is for them to be able to upload and access files, communicate back and forth through a shared mailbox (similar to a listserv), and access a SharePoint site to see our calendar and other simple info. Would Microsoft be able to support this or will it cause issues?