Actually the mall booth idea would work...She could do the same thing -- take pictures and do the drawings from those...They have those booths in the malls around here sometimes. She could even have a digital camera there so that she could take pictures of people there, and charge a few dollars extra for those ones...And then have a turnaround time of 7-10 days...People would then pick them up or have them mailed. Then people could either bring their baby pics or their artistic pics, or whatever, OR have her take a pic & make it...
That's just my rambling...Good luck whatever you decide!