A.L.
Our son LOVED Minecraft and had a great time with it. One thing to consider is that a youngster can interact with others through voice and through typing. The program has filters set up to screen out unsavory language in theory, however it's not fool-proof. One of our son's classmates set up a private server where the only people who could access it were those whom he (or his parent) approved. That might be an option for you if you want tighter control over whom he interacts with online. We did not go that route because our son was a little older than yours when he began using it, however I could see why you might want to filter a bit more, with a pretty young kid.
I just realized I didn't answer your first question... I don't know how to answer it, actually. In any case, I hope your kid enjoys it.