I purchased and downloaded Minecraft for Mac directly from their website with little issue or hassle in about 5 minutes (though I can see having it tied to a steam account being convenient if you have one already) a couple of weeks ago. There are some alarming parts that I was not totally expecting (monsters attacking during the night in the world, and Endermen, which make some really creepy sounds), but otherwise the game contains no blood or gore. This game does allow you to connect to multiplayer servers (provided you already have the server information) and there are no filters on text chat while in-game, however. I'd suggest doing a quick search for parental reviews of the game or checking their wiki for further information.