Part 4 of the Scout Photograper badge (still photography option) includes the option to "Describe the basic functions for editing digital images. In particular, explain the differences between cropping and zooming, resizing and stretching, and camera orientation and rotation." This activity suggests a way to achieve this.
What I've done here is to try to word the descriptions in a way that can be understood by an average 11 year old. Some of the photographers among you may question my explanations - that's fine with me.
Computer(s) with photo editing software installed - the simpler the better i'd say
Sample photos to edit
See attached PDF