Based on what you've written, that your DS wants to study geology, doesn't like reading from encyclopedias, and I'm assuming also wants geology-related labs, I don't think Sonlight Science G will give you what you want.
It is labeled as "geology, physics and origins", and it is really just a mish-mash of different things, not specifically focused on geology at all. I own six of the seven books (not counting the TM) used in that program, including the two TOPS lab books (and supplies). If you look at the book list, only one of the books used is specific to the study of Earth science/geology, and it is the Usborne Encyclopedia of Planet Earth. So, it's just an encyclopedia, which you said you don't want, and only about 150 pages, not enough to last a year. Cool Stuff 2.0 (talks about technology) and What's Science All About (another Usborne volume, a broad summary of biology, chemistry, and physics) are neat little books, but they were below the level of my DS last year as a 5th grader; he actually scoffed at them. They're both full of nifty info (for a younger kid, perhaps) but its just snippets, nothing in-depth. Another book (and a DVD) in the program talks about evolution vs. creationism, and the last book is about life science topics like botany and ecology. The two TOPS books are chemistry-related (Analysis and Cohesion/Adhesion) - again, not geology. DS used both of those TOPS kits last year, and we liked them pretty well, though. Sorry, that's probably not what you want to hear.
Sonlight's science programs for level G and below try to cover lots of things at a high level all in one year and the output is quite worksheet-y (fill in the blank, matching, etc.) That appeals to some kids but not others. The TOPS labs are usually pretty good but you don't have to get them from Sonlight, you can buy them directly from the TOPS website and I've seen them on Amazon too.
I can recommend the Rocks and Minerals TOPS book with kit, as a supplement. My 6th grade DS is using it this year and he loves it so far (about 4 weeks in). He can do it independently. We're also using Elemental Science logic stage Earth/Astronomy (which you said you didn't want) and supplementing with CPO Earth for extra reading.
Hope that helps some.