Hands-on projects and telling the myth behind each constellation are fun and engaging ways to teach children about constellations. Have the children draw the constellation on black paper using a white or silver marker or help the children create a 3-D model of their favorite constellation using marshmallows as the stars and toothpicks as the lines that connect different stars.
A good family activity that teaches children about constellations is taking a trip together at night to a field or park that doesn't have streetlights or other light pollution. Bring along a map of the stars, and use the map to locate stars and planets in the sky. The map can be from a book, printed from a website off the Internet, or loaded from a phone or tablet application. Ask the children to pick a constellation they want to find before heading to the park, and work with them at the park to find that constellation in the sky.
A trip to a local planetarium or observatory is another good way to teach children about constellations. Many planetariums have staff members that are available to teach children about specific stars. Some observatories allow people to use their telescopes to see stars and other space objects.