Mom and Dad, you two are a huge part of the show. One of my all-time favorite things to do is take pictures of the bond between a parent and his/her child.
Dads: Please wear a solid-colored shirt that looks casual yet dressy.
Moms: Keep the design simple and the colors neutral. Your hands will appear in the pictures, so make sure you don't have chipped nails if you're wearing nail polish.
I believe that neutral/tan, cream and blush, or solids/blacks are the colors that work best for family portraits. Keep in mind that the new baby is the main attraction, so avoid using distracting patterns and loud colors.