I've never used Mindstorm but I was a kid, way back when. This is clearly the way to go. You want them to come back the second day after all.

Another alternative would be making little games in Flash. Actionscript 2 was really easy to learn and you get to make things explode! You can trick them into learning...

If you want eye catching animation, something based on Flash would seem pretty sensible. If the metrics could be made available in XML, you could load it into a Flex application. There are a lot of graph and chart components available for Flex these days, eg http://demo.quietlyscheming.com/drillDown/app.html. Not all of these components are free mind you but at least the FlexSDK is open source now.