Challenge your child to find a small figure or sculpture and take a photo that makes it look like a giant! Place the figure in front of different backgrounds and position the camera lens in such a way that the object looks very large against it. Shooting from below or down low will usually accomplish this view, so move around and experiment.
Other perspective tricks to try include capturing a large building between 2 fingers, creating a photo that looks like the setting sun or rising moon is sitting in a wine glass or flying into a basketball net (caution: don’t shoot directly into full daylight sun as it could damage the sensor on the camera and/or hurt your eyes). There are endless opportunities for really fun perspective photos!
For more inspiration, do an image search for "forced perspective photography".