Nick Nolte could play Nancy Grace.
Here are my picks for Casting:
Casey Anthony:
The Doctor chick from Sons of Anarchy, Maggie Siff
The Grand Parents

I'd take Joey and Mary Jo Buttafuco FTW, Alex. These two have the same chemistry. They also always seem like they are hiding something, so they don't really even have to act. Just tell them the movie is actually about their story, and they won't realize they are playing George and Cindy Anthony.

Nancy Grace is a tough call. While, my first impulse would be to cut to a snapping turtle, I'd have to say that I'd go with Sue Ellen Ewing from Dallas circa 1985

She has the bitchyness and self-entitlement thing down pat, and she has the accusatory hollier than thou status in her facial expressions.
I tried really hard (well okay, actually about 2 minutes) to find some one in the current world who embodied the big-hair and self-importance of Nancy Grace, but found that all actresses who could have pulled that off were from the 1980s, so you are stuck with Linda Gray in the modern times trying to revisit her Sue Ellen role.
(Man, I loved that Hank Williams Song "You aint Sue Ellen, and I ain't J.R...)

This dumbass, you just put a cowboy hat on this motherfucker (below) and you got yourself an actor to fill the role of the self-promoting jack-ass that doesn't really know shit and brought nothing to the table. For Doctor Phil, the role is semi-autobiographical.

Thats the major players I'd cast.
Also, you'd have to put Melissa Gilbert in it, because contractually if it's on lifetime, then she has to be in it (I think)

plus, she has nice Ta-Ta's.