1Blockoff is a semi vanilla survival server with a chilled non-pg community, but not overly explicit either, so it still fits a mix of age groups. You'll need to register when you join before you can use commands, and after that auto-login makes things easier every time you come back.
The server has custom terrain, a custom Nether, and a custom End, plus Slimefun with multiple addons for players who want a bit more to do than plain survival. There's also a server shop, a public XP farm, and Towny for players who want to settle down, build up a town, and play in a more organized way.
It also has a live map and a wiki with actually updated info, with more being added as the server grows. 1Blockoff is kept on the latest version, so you're always playing on current updates instead of getting stuck on old stuff.