Typically - If you have any way of figuring out who the child really is by name, address, area etc., then you must work to protect that info. On my baseball teams site and our scout site we had two things that we had to do. First is to notify parents of the rules and either gain their permission or password the section that had the pics and/or information.
We chose to go with passwording. This makes it up to the parents as to who they give the password to.
At most schools, you have to have parental permission to post a pic and then most still use no name with the pic. Example: At my daughters school there is a picture of some of her art work that we recognize that leads to her pic and stuff she has done. No names are used. This still can lead someone to her school but there is no name associated with the pic.
The link below is some info on the COPPA. Children's Online Privacy Protection Act
IMHO. As long as the site listed a statement about their protection of information with some rules to only post pics with "trailnames" and there is no indenty info available on the parent's profile, I think the site would be following the guidlines and the kids would be ok. Again IMHO
It is still up to the parent as to whether to post the pics or not.
I hope this helps.