Eh, the bigger problem with lost children is their habit of hiding or wandering back into cleared areas. Fortunately, they don't tend to wander far. Lost Person Behavior guidebook puts a 4-6 year old child at a 95% range of 5.1 miles in dry territory. That doesn't change dramatically until you start approaching teenage ages.

I've posted a few criticisms of IR already in this thread. There are a narrow range of environments where it's helpful, and there's a tradeoff between image quality and flight time -- you can have good flight time and terrible image quality, or good image quality and terrible flight time.