CW was not a normal father and not a normal human being. He is evil, selfish and placed his own desires above those of his family. Its difficult for normal people like us to think like a monster.
I think CW panicked at the thought of killing Cece and Bella in his house. His adrenaline and cortisol levels were sky high, especially after Bella saw him hurting her mommy. She probably cried and begged him not to because she knew something was horribly wrong.
He had likely thought about killing the toddlers and planned their deaths but when it came to the crux he froze for a short while. It was not as easy as he imagined. He used the driving time to get rid of Shanann's body at the oil site to think about how to dispose of C&B.
I think after murdering Shanann and his unborn son, he attained some sort of chemical dopamine rush to his brain, a powerful sense of bravado, and he prolonged the moment of murdering C&B until he disposed of Shanann's body.
Ultimately he decided the toddlers, especially Bella the witness, were a liability and he murdered them.
I think its a simple case. CW is a vile, selfish monster who decided his life with a new squeeze and Audi Q7 were more important than the lives of his wife, unborn son and two little girls who called him their hero.
He's far beyond any redemption, bible studies or finding "Jesus". He's a hollow, mud creature and has no soul.
moo