I've been using Private Internet Access (PIA) VPN for years and have not had any issues with them. They have clients for iOS, Mac, Windows, Linux, and Android. I believe one license allows 5 devices to use the connection at the same time.
I find it easy to use and have got my wife and parents to understand how to use it. On your iPhone, it will install as an app and you can either enable the VPN through the app using the toggle switch or through the iPhone VPN settings. On your Mac, you install it as an app and it will add an icon to the menu bar. You can click on that icon to manage settings and to enable/disable the VPN.