Sometimes Yogi Bera's saying you can observe a lot, just by looking conveys a lot of wisdom. The night sky has a million stories to tell your kids. All you have to do is take them outside, and look up.
You may not be at Hirsau Abbey, and won't have a cool interactive map of the constellations, but 15 minutes prep on the major constellations and their stories will give you an hour of fun with your kids. A pair of binoculars will add a surprising amount to the fun. For example, the Pleiades (the "Seven Sisters") is easy to find, and even low power binoculars add to the viewing experience.
Time with your kids, with the TV off for an hour. That's not broken.
Picture via the always amazing NASA Astronomy Picture Of The Day.
UPDATE 7 June 2009 15:08: Via Phlegm Fatale, here's a guy who really likes to look up. Great to show your kids, and then take them out to look at the evening sky.
I can't find a way to link directly to Phlegmmy's post, so I've embedded it here.