Mobile Photo Van

You set up a truck (yeah, a lot of these start that way) with the lighting and backdrops you need to take good kid pics.  Then you drive around to your clients houses taking the photos right then and there.  The benefit is the parents only have to keep the kid happy for a few minutes rather than hauling them through the mall, waiting 20 min for the last group to finish and then trying to coax a smile out of a fussy child.  You wouldn't have to worry about keeping clothing clean or hair falling out of place if you had just walked out of the house with your perfect child only 15 sec before the picture was taken.