Overview -- The Children’s Online Privacy Protection Act (COPPA) affects websites that knowingly collect information about children under the age of 13. The COPPA regulations are incredibly complicated – if your web site is available to children under the age of 13 it is my recommendation that you contact a knowledgeable attorney to review your compliance with COPPA.
In reply to your post; you absolutely need written permission from each parent before you can post any information (including unidentified children in a picture) before you may post any information on a child under the age of 13.
Do Not think you will fly under the radar, or be too small to deal with. The government enforces COPPA more actively than any other web related law. For instance, the girl scouts paid a huge fine to the FTC for their violations. Many smaller sites like yours have also gotten into trouble.
Please be careful about posting information without signed, explicit, parental approval!