Google Voice is free. The google voice dialer app makes free call over the Internet. They may also want Groupme, a common group messaging app. We give them one of our phones when we upgrade. The older phones get passed down to the younger kids, when they are old enough.
The key for the setup for us is Qustodio. Being able to enable, disable, and set time limits for apps, filter web content, and see most of the things they do on their phone makes a big difference.