Play with your child in front of a mirror.
Make faces and move your bodies in different ways. Hide from the mirror and try to sneak up on it. Stand at different places in the room and see if you can see your child without your child seeing you and vice versa. Then go on a hunt for other surfaces in your home that make reflections.
Try doors, tables, walls windows (both sunny and shady), and any shiny things, like kitchen appliances or even spoons. See how many places you can find that make your reflection.
What is different about these reflections from the ones in the mirror?
For an extension to this activity, provide drawing materials and invite your child to draw a self-portrait from his reflection.