Another option is a neighborhood wifi system coupled with TCP handhelds. Problem with that is that it is dependent on the central hub. If it goes down then there is no communications.
As a professional computer nerd, while that is technically intriguing, seems too much can go wrong given the stated mission.
In ARES/EMcomm, we use packet for winlink emails when we need to accurately relay detailed information up the chain of command.
This is ideal for situation reports, or administrative tasks like authorizing resources, that benefit from a "paper trail". Even though this is done on the VHF amateur band, sending a simple text email via winlink requires some kind of PC, digital interface (TNC+cables) and an appropriate radio (duty cycle and technical specs are beyond the scope of this thread).
For quick tactical communication, voice (phone) over handhelds is still king. "Check point A, this is base. Has the fire truck arrived at your location?"
For anything involving modern smart phones, if you are willing to depend on the devices and their respective mobile networks there are a number of solutions, including Zello. For a random group of neighbors, chances are 2-3 mobile cell phone carriers are involved. During an emergency some or all of those might be disrupted.
This is a tough spot for unlicensed folks.