The night isn't a quiet place. Bring some lawn chairs out in the yard and gather your family as the sun goes down. Listen to the different animals -- birds, bugs, bats and amphibians -- that liven up the dark. Using a nature guide for your area, see how many different critters you can identify by sight or sound. When it gets totally dark, turn on a porch light and stand back as moths flock to it. Use a digital camera to capture images of the different types of flying bugs that show up. Then use The University of Georgia's Discover Life tool to identify your moths. The mapping feature will let you see where else around the world they live.
If your family gets really engrossed in night life, consider pitching a tent for a backyard campout.