Why should having a child give any sort of leniency? Actually the aim of harming that child should increase the penalty. I believe in equality, giving discounts on crimes because family just seems absolutely unquestionably evil and immoral.
If we really think of it, shouldn't single person get leniency because him being in jail doesn't hurt others. So that can be considered in thinking about planning of crime. As others clearly aimed to hurt their families and friends by getting in jail in first place.
I would also expect leniency if you got the child after you were charged, even though that implies people could just get kids to look for leniency, there is the idea that once someone gets a child they calm down and become more cautious. Maybe not so important in cases of non-violent, monetary crime.
However as it is commonly thought in society, and backed up by science ( https://www.psychologicalscience.org/publications/observer/o... ), that women take on a more nurturing role for the children and the absence of a mother would be more traumatizing (statistically, in the case of my son he freaks out if I leave but doesn't care much about the mother), the father can expect less leniency than a woman.