I'm currently introducing my 10 year old niece to programming using ComputerCraft, a single player mod that introduces several programmable objects in to the Minecraft world. Installing is a bit of an exercise, because it requires Forge, but it is otherwise worth it. I recommend using MCPatcher to load Forge, then just drop the ComputerCraft zip in to the /mods folder inside your Minecraft data folder.
One of the downsides of the diversity in the Minecraft modding community is that it can be difficult to identify the "best" way to do something. New tools come and go, and compatibility wanes when new releases hit.
http://www.computercraft.info