I’d err on the side of caution, especially given that these are children. On the other hand, I have used photos of children taken decades ago, in an historical documentary, because the images told a serious story of poverty and survival. I somehow feel there is a difference, because my use of the pictures had more relevance to the Truth of these kids’ lives than a PSA. But maybe if I saw the script of your PSA, I’d feel that the same way about your use.
If you can persuade the powers that be that using actual photos is a bad idea, this could be a great opportunity to do some casting, art direction and clever costuming — make some 2007 kids look like 1980s kids, shoot it in full color, freeze frame and sepia tone it.
Or just find some smaller-town high school class reunion organizer — he/she might be able to get releases from almost every single person in a class photo, and if any aren’t available you could just photoshop in somebody who will sign. Lots of work either way.
— Bob C