We used the three-volume God's Design physical science series, plus kits, plus Mythbusters, plus The Art of the Catapult My oldest is planning on majoring in physics next year, we sure had fun!
The K'Nex kits were BIG hits here, the boys played with them endlessly. There is a Levers and Pulleys one and I think a bridge one. They ended up building out of those and regular K'nex a message system between all their bedrooms, even up and down the stairs. LOL
You can learn a LOT by watching some selected TV shows. My kids have learned a lot of physics watching Mythbusters and Punkin Chunkin. :-) We really, really recommend The Art of the Catapult as well.
I have two other books that would probably work for your ages---Physics, Fun, and Beyond are easy-to-build projects that use recycled materials, and the book Thinking Physics: Understandable Practical Reality is very, very good at using physics principles in plain language to explain nearly everything.
IMO chemistry and physics are just the MOST FUN to do with kids. There's nothing quite so satisfying as lobbing oranges over the fence. :-)