The indispensable Bad Astronomy blog, points to this great site:
Science: [ So What? So everything ]
This site, run by the British government, is a great way to promote science. I wish our government, here in the U.S. took similar approach, and started promoting real science, instead of woo and nonsense, like the NCCAM, for example.
The site has a great section for parents, with ideas on how to answer some of your children's questions and how to communicate science to them effectively.
As I am on the topic of educating children, another great site has a multitude of resources for parents, who want to expose their kids to some quality science education:
100 Tools to Make Your Kids Math and Science Stars
It's good to start early (not too early... let them have their childhood!!!), and keep pushing science and reason in their lives, since most of the public schools in the U.S., society in general, and peer pressure, look down on scientific education.