Okay, let's consider this preposterous claim, as valid.
SW comes home at 2 am, and kills her children. (Having been 16 weeks pregnant myself, at 2am after travel, you barely have energy to get to bed, but maybe Thrive gives you super human energy). Okay.
CW bursts in to save the children, who are already dead. He, in a fit of anger, or trying to get her away from one of the children, kills SW, accidentally.
He panics, is not thinking, so he automatically puts the bodies in the truck, puts the girls in an oil tank, and buries SW in a shallow grave, goes to work, like nothing happened.
The friend calls CW, looking for SW, he doesn't explain what happened, goes home, makes up a fictional story. Goes on tv, asking for them to return.
When questioned, he talks to his Father, and explains what really happened, and makes a statement to the police.
Seriously, there are so many flaws here, not even a jury from Pinellas county could go with this.