flash. once they learn the individual parts they can learn how they all contribute to creating a photo. younger kids just need to know the parts they use the most like the toggle, the flash, the shutter release (button you press to take a photo), the lens and the on/off switch.
a scavenger hunt at any age is a great way for your child to look for photo ops. create a scavenger hunt of about 10-20 things for your child to take a picture of. if you are out and about in the car they could snap pics of street signs, or mail boxes that they see out of the window. 