My soon-to-be wife isn't terribly familiar with business, or farming, either.

A few topics we've covered, and some I plan to cover in the future, and some things she has been curious about (she listens patiently, but can only listen to me for so long ...).  Perhaps more general than topics which you were considering if you were wanting to focus on farmers themselves, though.

   -- accrual accounting, interest/carrying costs and the concept of paying for stuff 6 months before you need it and getting the money 6-12 months later
   -- loans, callable vs. term, secured and unsecured debt, types of security
   -- concept of net worth and having that net worth invested (the 'why can't you get a simple statement from the bank showing how much money you have?  Because I sure don't feel like you're worth $xxx'). 
   -- net worth and 'mark to market' concept - imputed gains/losses on balance sheet, vs. actual incurred gains/losses 
   -- tax structure for the self employed vs. wages vs. investments
   -- buying land and other appreciating assets - loans, theoretical ROI, some explanation of why did you just sign a $1M land mortgage, etc.
   -- 'external costs' - stuff that someone pays for, even if you don't (like when you borrow some machinery, or someone borrows yours, or even all the way into the external environmental costs)
   -- depreciation, and buying 'stuff' that depreciates   
   -- insurance - crop insurance, liability, property, buying health insurance on the individual market
   -- concept of the futures market/basis/margin calls
   -- basics of weather/weather forecasting (not straight business, but it sure affects us all - probably some different typical weather in the PNW vs. Midwest, though)
   -- the Farm Bill bird's eye view - what the 98% get out of it (food subsidies, stable markets, lowered external environmental costs) and how the rural population/farmers benefit (what is the FSA office, again?)
   -- farm organizations, lobbying, the policy process
   
The teacher-types sure are nice people.  Or at least I'm banking on that when I get married.