When shopping, explain how the card works and when the bill arrives, explain it again. Due date? Check. Payment options check? Check. Interest rate? Check. Grab a calculator and show them what an interest rate is — in real dollars. Talk about what happens if you don't pay off the balance in full and make a rule to always do so.
There is such a thing as moving too fast, and in my opinion, I think all this education can be done without a credit card. You can use your own credit card and explain the bills to them. To really let the lesson hit home, you can charge one of their purchases to your card and use that particular buy as an example. Children not only have to learn how to use a credit card, but they also need to learn the bigger lesson of how to live within their means. They can pick this up by simply mimicking you so you need to have the right attitude toward money in order to lead by example.
What do you think — is giving kids credit cards a good idea?