Will offer some initial comments to get things started.
Most email programs (e.g. Outlook) permit you to establish a contact list targeted to a select group of individuals.
So that capability may already exist and will cost nothing to implement per se. Just someone taking the time to create, verify, edit, and maintain the mailing lists. Those lists can often be kept in a separate database or other source location.
Texting and phone calls are likely to be more problematic. Which is why similar groups relay on phone trees for mass notifications.
Another concern is that your service providers may flag the outgoing information as spamming - and block your email account/phone number accordingly.
Any universities or colleges nearby...