I would have the kids, if they can use a parents digital camera to take some images of either thier pets or favorite toy,then teach them how to bring the picture into Photoshop.They could then use many of the artistic filters it has.Perhaps get them to learn how to add fonts ofr a name.Adding borders. I see you posted this in the Photoshop forum as there would be some other great ideas in there also. I would start them off with smaller file sizes so the wait time on the effects is reduced.

"The happiness of a man in this life does not consist in the absence but in the mastery of his passions."