Deborah, do you really want 'that' wide of a lens for kids and portrait shots? Generally I would recommend an 85mm 1.8 for a lot less money that would get you into the right focal range for proper facial depth, without exaggerating the nose and features, as discussed before. Using 16mm on a persons face would not give optimal results, and would be a lot of $$$. I'd suspect that you could get much better light gathering and save a pretty penny by going with an 85mm 1.8, and you'd keep the features looking proper.
Just my opinion. That and with a 16mm shooting portratits, you'd be too close to the child / baby / adult for them to be able to relax and act naturally.
Adam