Why wouldn't it be legal?
There is no law that says a business or people cannot post the names or pictures of people - even minors. There are laws restricting what GOVERNMENT (police, schools, records, etc.) may release about a minor, but very few concerning what a private person or entity may reveal.
It sounds as if these are kids that were involved in alleged problems or crimes at the mall and they are trying to get more info. The parents of the kids pictured might have a claim for civil damages of some kind against the stores or the mall if they did nothing wrong, but there is not likely any law that prohibits them from posting the request.
- Carl