Who to Choosing Between programming language?

[mathking]

I don't have any simple, fun C++ tasks for kids to do on their own, but I have another for Java: Robocode. It is a great way to learn Java programming while you program virtual robots. It is free and cross-platform as well.
http://robocode.sourceforge.net/

Alan highlights another important thing to consider: version control. If you are going to have multiple programmers working on the code for the robot, version control is very nice to have. I will disagree a little with Alan, in that I actually find that in general the version control systems I have seen for Java are easier to learn than for C++, but there are many good options for both. In fact, the ones we have used will work for either language equally well.