Economics for children

A loyal MR reader asks:

I would like to start introducing my daughter (age 8) to the concepts
of economics.  She is a voracious reader so I thought that might be a
great place to start her thinking like an economist (on the other had,
she dismisses anything her father tells her out of hand)
 

Do you have any suggestions on books that would be great for a 3rd or 4th grader?

Any suggestions?