I am wrapping up a new pc build for a friend who has 8 and 10 year old boys. They love minecraft, spore, and subnautica, and mom is working on getting the latter two of those right now (they've played them on xbox previously). I was going to try and load up some of the free stuff on steam (or elsewhere!) but I really have no idea what's child appropriate for their age range, and I was hoping some of you gamer parents could weigh in on suggestions? If not free, stuff that's super cheap?