I have been thinking about this theory...
So GA leaves for awhile because he said there were financial issues and mainly he was dealing with his daughter being a single parent.
After the gambling, and what ever else, Casey and Cindy were glad he was gone. But then they find out this can't be permenant because a divorce would be too costly (alimony and half the house Cindy has paid for).
Cindy and Casey decide they need to get rid of GA from their lives, so why not have GA come back home and really get rid of him. They want it to look like an accident. Well he works his job is a pest control man, they think "those chemicals are dangerous" maybe find out whats in pesticide. Or maybe they can set GA to fall with his bumb knee.
They even talk about after GA is gone, Cindy can get a place close to her parents. Casey can stay in the house with Caylee and says she can make the mortgage payments.
I would be very interested in whether or not GA might have a life insurance policy.