As much documentation as possible should be provided when filing the application. Most decisions are already made BEFORE the interview.
If a person has sufficient evidence to prove they will not overstay, they stand a shot at getting a visa. If you can't prove it, your not getting it... Think of it as everyone is automatically refused until they can change the CO's mind.
Honestly, (in my opinion only), I feel that having a child in the US is a negative more than a plus when it comes to getting a tourist visa approved.