How to control a motor with a photoresistor
OK rather than continuing comments I'll answer here.
For kids only five years old this will be a bit much I think.
I'd start with just batteries and light bulbs... How do you make the light turn on?
You can then do some series and parallel stuff.  But even that may be over the top for some.. maybe best to just let them play around..  (How many different can you get a light bulb to turn on.)  If you wanted you could add some LED's to the mix.  (Maybe with the current limiting resistor soldered onto on leg and covered with heat shrink.)  I can think of lots of fun things... but again may not when they are only 5.  (A red and a green/blue LED in parallel would be interesting.)