If want to inspire your kids to start measuring stuff get them to check out the site The Scale of the Universe 2.
It's interactive and takes you on a journey from the biggest thing known to man to the most tiny!
You could send them on a treasure hunt - try and find Jupiter, the Grand Canyon, the Titanic, an egg, a red blood cell and a helium atom. Each object will pop up with more information when you click on it.
Fantastic resource which we just had to share.
Although Alan is still a little overwhelmed by the size of lemons in NZ ...