Learning about stocks

Don't get me wrong, I'm not a "heavy trader", but I do have a few shares of stock in several different companies.  When they do well, they pay dividends, and a few companies out there also pay their stockholders with other rewards as well.

One of those is is Darden.  Each quarter that they do well, I receive a $5 gift certificate to use at one of their restaurants.  Darden is the parent company that owns Red Lobster, Olive Garden, Longhorn Steakhouse and 4 more.  Since Red Lobster and Olive Garden both run coupons on a regular base in the paper, we combine the certificate with a coupon and usually end up getting one meal free. 

Now that the girls are old enough to somewhat understand stocks, I plan on getting a few shares for each of them.  This will be a great way for them to learn about stocks, the market, expenses.  I'm still looking for a good book that will explain it on their level.  Any suggestions??