Could it be done in the Doc's office? One kid in the orthodontist's chair with the camera at the base of the chair (toward kid's feet shooting up), Doc on the right side. Mom on the left side. Shorter kid in front of Mom and tallest kid on a rolling short stool in front of short kid (or maybe in front of Doc). Not sure if you could get your lights, etc. in the office and be able to isolate any distracting stuff, but maybe worth a trip to Doc's office to check out???
You might snap a funny one with Mom handing the Doc a handful of money. Doc might not like that one though...
