Yes, I agree! If it was just the "God of the gaps" issue, that is easy to address. The difficulty is really the mocking tone toward scientists and Christians that see evidence for more than micro-evolution and explaining to our kids why a Christian author would have such a rude dismissive attitude (and the fact that we're then implicitly encouraging that attitude in the Challenge kids).
The book is also kind of old and scientifically out of date (originally written in 80s and republished in 2011 with no mention of what's transpired since then...human genome project etc). I am hoping to put together a study guide of some sort to use alongside it. It would be so helpful if they would read The Fallacy Detective first, because It Couldn't Just Happen would be perfect material for applying those principles! PM me if you're interested in whatever I put together or have any ideas and I'll keep you in the loop.
If you wanted to add in another book to go along with Chall A that would show the range of views Christians hold and also demonstrates a more charitable attitude, you might try the Haarsma's Origins: Christian Perspectives on Creation, Evolution, and Intelligent Design. I'm planning on reading that with my son.
Glad to have you connect with us here!