I can't help much with the space stuff, but my son was a complete dinosaur geek from the time he was three. In third grade, his absolute favorite dinosaur books were the series "Introducing Dinosaurs", published by Child's World, most of which was written by Janet Riehecky. They're out of print and were expensive, but since I had most of them memorized by the time he was in third grade, it proves that we got our money's worth. You may be able to find them used on Amazon. The series has apparently been updated (a lot of information has changed in the last 20 years, like the whole feathers thing) and continued, and is now available in ebook format. Every book included the pronunciation for any dinosaur name, which I found really helpful.

(My son, who just graduated from college in December, is moving across the country next week for his first real job. This afternoon he told me that he was leaving that set of books in my care. He threatened to abandon me in the worst nursing home he could find if I dared to get rid of them. I won't! I promise!)

Dougal Dixon's books are always a good choice, and paleontologist Jack Horner has published several children's books about his excavations. His biography, written by another great kids' dinosaur author Don Lessem, is for elementary-age kids and really inspirational - Horner was dyslexic and never went to college, yet he's the guy who Michael Crichton modeled the Jurassic Park paleontologist after.

My son also loved the fictional world of Dinotopia. In addition to four gorgeous picture books with fantastic illustrations by James Gurney, there are elementary-level chapter books about Dinotopia and several suitable for middle schoolers that were written by Alan Dean Foster.

(As it turns out, my son's mom is also a dino geek.)