I have recently completed 2 portrait commissions of a little girl, one in watercolour and the other in pencil.
The challenge is not to overwork the shading in the pencil drawing or the strength of colour in the watercolour in such a young person.
Likeness is an obvious objective but breathing life into a pencil or watercolour portrait is so important. A sense of immediacy is suggested by the hatched shading lines. Normally I avoid drawing teeth but these baby teeth were irresistable!
I worked from some very good photographs taken by a professional but even good mobile photos make good reference.