Check out Zoom on www.pbskids.org. They have loads of science ideas. If your library has a some of the videos you could watch it with your kids an probably get some ideas there too.
Our kids loved the bottle rockets (alka-seltzer tablets are used). It was the most popular station. We were fortunate to have a company, Bayer, Inc., nearby and we approached them about having a family science night. They sent out six of their employees (chemists/scientists/lab workers), with ideas to explore science, equipment, the whole "sha-bang" and they put together and ran the event for us. It was excellent!!!!!!!! They donated everything and their time. We gave each of them a gift card for dinner as a thank you.
We are hosting a Family Science Night soon and are working out which activities we want to provide. Any ideas? We also like to have something(s) to send home at the end of family education nights - any suggestions for that?