Wait until the light is just so. It'll probably be right about when you should be making supper, which truly will make this that much more fun for your children. Mom's willing to ditch being a nag and telling us to give her ten minutes to get the food in the oven? Sign me up!
Warning: make a crockpot meal on the day you try this, because if your kids are anything like mine, then you will NOT get anything on the table before your husband gets home. But you will have some silly, giddy kids who have cracked you up with their creative animals and convoluted plots.
If you don't have the benefit of NW shadows in the winter, try a lamp in a closet. :-)