Place the cake mix, flour, ginger, and cinnamon in a large bowl; stir to combine. Add the eggs, oil and molasses. Mix with a wooden spoon until well blended and all dry ingredients are moistened. Chill, covered, for at least 4 hours or up to overnight.
Preheat oven to 375° and spray cookie sheets with nonstick cooking spray. Position racks to upper and lower positions of oven.
Sprinkle a work surface with a thin layer of flour. Set out rolling pin, 4-inch gingerbread person cookie cutters, metal spatula, and cooling racks.
Remove the dough from the refrigerator and divide into fourths. Place ¼ of the dough on floured surface (cover and return remaining dough to refrigerator). Flour the rolling pin and roll dough to ¼-inch thickness. Flour cookie cutters and cut out shapes. Transfer dough to prepared cookie sheets with spatula. Re-roll any scraps, then repeat with remaining dough, rolling one fourth at a time.
Place one sheet on each oven rack. Bake for 4 minutes. Rotate the sheets (place the sheets from the bottom rack on the top rack and the sheets from the top rack on the bottom rack. This ensures even baking). Bake for 4-7 minutes for large shapes or until center is puffed and sinks back.
Remove from oven and let cookies rest on cookie sheets for 1 minute. Transfer with metal spatula to racks and cool completely.
Prepare vanilla icing: Combine the powdered sugar, 2 tablespoons milk and vanilla extract in a medium bowl. Stir until icing is well blended, smooth, and spreadable, adding more milk by teaspoonfuls if consistency is too thick.
Decorate cookies with icing and candies or raisins, if desired. This may become one of your favorite Christmas recipes!