There is a great new website dedicated to teaching schoolchildren about our judicial branch of government.
Here is an article in the Washington Post about the site and the online games: http://www.washingtonpost.com/wp-dyn/content/article/2009/10/01/AR2009100103888.html?wpisrc=newsletter
And here is a link to the site. It has more than just the games, but they may just be the "hook" to get your kids interested:
http://www.ourcourts.org/