4
put them on a LAN (not connected to the web).
First, whatever mods you install, make sure you install lots of smilies!
install news mod, a gallery mod, mylinks, and mydownloads.
give them a digital/video camera, a drawing app (or kids flash animation!) and coloured pencils, a pen and notebook (as in paper). provide a scanner.
encourage them to keep a diary and to take lots of pics.
They can post the diary in news, upload pics from the camera to gallery. scan, manipulate and then upload whatever gets put in the notebook to mydownloads, add links to their friends' sites to mylinks...
If that doesn't grab their attention, you could always have them document a real life project (building water rockets/what-have-you)
Never let a man who does not believe something can be done, talk to a man that is doing it.