To protect your credit card online at Pirate101.com set up a Master Password.
Do not give your child the email address or password used on the Master Password.
Do not allow your child to have access to your credit card or credit card information.
To learn more about keeping your child safe online, here is a list of articles and websites that will encourage discussion and provide more tips and information.
There's also an online consciousness contract that you and your family can sign to help with awareness and behaviors online. This contract is located at The Parent / Child Digital Consciousness Contract