I've been looking for something like this to coordinate volunteers. Per seat pricing makes it impossible for us to use any existing tool, so we stick to WhatsApp which is productivity hell.

Well, there's one more hard requirement. We need the tool to work in Spanish. It's unbelievable how many apps refuse to localize their app, taking into account how easy it is too keep a good localized app in many languages. You're early stage, so this would be a good time adding i18n, l10n. If you want help dealing with that, I can help.