C, my main concern is putting any type of personal information on the Internet. In your group, neighbors and family heck yes but not to the open world. It is too easy for someone to set up a fake website/group.
When you download the app there is no telling what else comes with the application. Most smart phones have the ability to send text to multiple folks at the same time. Set up a group “call-up” on your and your groups/families phones.