Oooh, questions, good thread! I'm going to lurk and see what help I can get for my DD6 in this area!

The only thing I can add that might be helpful is that you might want to check out www.electrowiz.com for science stuff. I've heard good things about it, and I'm going to try it out myself for the summer. Apparently the books and kits are well packaged and interesting for the kids.