I love the description of John and Fanny's son in chapter 1.

...such attractions as are by no means unusual in children of two or three years old: and imperfect articulation, an earnest desire of having his own way, many cunning tricks, and a great deal of noise

Having a son who has just passed this age myself, I think it is such a spot on observation about children.

As we read through the novel, there are other descriptions of small children and how they act. It's hard to tell though, sometimes, whether the view of children and their behaviour is more realistic, more cynical, or both.