I am looking for a small, kid-friendly development environment for
games, modeling, etc. Something similar to Micro Worlds.

I'm going to give my 12-year-old son a computer for Christmas. The host
OS will be Linux. I will set up a VMware Windows box inside the host.
Next time a virus bricks his Windows 'box' I'll simply clone an instance
from the mother egg and he's off and running again. Just a dad's answer
to a recurring problem.

It's also a wonderful opportunity to get his head into Linux space. He
will be able to use Open Office for his schoolwork. He's already wild
about several Linux games and he plays them on Knoppix whenever he can.
Now I need to find an IDE that facilitates development of simple
graphical games, and/or a simple graphical modeling program.

Any recommendations?

John