Long, long ago, man’s only source of light was the sun.
But the sun was gone during the night and during the winter there was little sun at all.
(Have children act out how dismal and cold it was without much light)

Then one day, someone learned how to create fire by rubbing sticks together and creating a spark.  Soon man knew how to build nice large bonfires.
(Have children act out sitting around a nice bonfire)

But when the winds and rains came, everyone had to go inside where there was no fire or light.  Some people decided to build fires in the middle of their houses but the fires often burned down their houses.  Then someone decided to build a small area of stone, where they could build their fire, so it would not spread to the rest of their house.
(Have children pretend to haul stones to their homes and build a fireplace.)
Fireplaces were great but people started to build bigger houses and it was hard walking from room to room at night without light.  Someone discovered that if they put a piece of wick into oil and light it with fire from the fireplace, the wick would burn.  They had invented oil lamps. 
(Set out an oil lamp for children to see)

Next, someone found that if they dipped a wick in hot wax, over and over again, they could make a candle and it would burn giving off light.
(Set out a display of various candles)

Someone noticed that often their candles blew out when they went outside, so someone invented the lantern, a nice enclosure for their candle.
(Set out a display of lanterns, including a jack-o’lantern.)

Eventually, Ben Franklin discovered electricity and then the light bulb.  Now we have all kinds of electrical lights.
(Set out a table lamp)  What makes the lamp light up?

Lamps were great but often men wanted a light in a place that had no electrical outlets, so some bright person invented the battery.  Now we can have light most any place we want.
(Set out a display of battery operated lights)

NOTE:  Please excuse any unintentional inaccuracy in this simplified version of the discovery of light sources.