Don't know much about Scratch but both DS10 and DD10 are into Minecraft although in different ways unless they are playing each other. DD is more into designing (skins, etc.) and likes it when strangers download her designs. DS is more into strategies (hence, all those youtube videos) and battles. I had to pay twice for the PC version so they would each have an account. The Pocket Edition for Kindle is nice as well and I only had to pay once since their Kindles are on the same account so all the software in the library can be shared.
I am very comfortable with un-monitored access to Minecraft at DS/DD's age and a couple of years younger but I would have been hesitant about introducing it to a four-year-old due to addictiveness/self-control issues.
