There’s a really interesting article in the current Mother Earth News about solar energy, including comparisons to other energy sources. You can read it here. It brings up some interesting points that are - I think - discussion worthy, in a way that kids will be able to understand. For instance,

“…while coal is the most abundant fossil resource, the total amount of energy produced by burning all the coal on the planet would only be equivalent to the solar energy that strikes the Earth every six days.”