Hi KevinAthans,
Welcome aboard! I just wanted to comment about a few things. Concerning this first thing I'll be rather blunt:
I just want to start making some money...
If you have outside sources of income to draw upon or are on full fellowship or your parents gave you a house or for whatever reason you are not hurting for money then just ignore this.
But if not then with 2 kids and a wife who wants to get her "doctorates," and after that you'll be getting your doctorates, then you need serious money. You and your wife do not want to be entering the full time job market owing $400,000 with training for jobs that have entry salaries of only $35,000/year. It's great to follow your interests, but make sure there's the kind of training mixed in there somewhere that allows at least one of you to get a job that makes real money, otherwise you'll never dig out of the debt burden.
You mentioned American history, thought I'd mention I'm in the middle of David McCullough's biography of John Adams.
Lastly, about Darwin, I've read a couple biographies and it seems to me that his naturalistic studies were already providing a significant push toward agnostic thinking long before his daughter's death. Do you have evidence leading you to suspect Darwin's tendency toward agnosticism only came after his daughter's death? In other words, are you pursuing this because it is something about Darwin that it appeals to you to believe, or do you have material evidence? From what I've read it can at best be argued that his theological doubts continued turning more toward certainty with the death of his daughter. I don't think there's evidence to support anything more than that.
--Percy