Thank you for posting, HeatherA. We had to go through the same with our son a couple of years ago. He'd had a passport since he was nine months old, and the first renewal when he was 5.5 years old was easy. The rules had changed by the time his passport was up for renwal when he was 10.5.
We brought his official birth certificate with raised seal, and his expiring passport. I believe we had to submit only one of them. It was were returned with the new passport.
from the U.S. Department of State explains it all.
On another note, minors age 14-17 also have to appear in person, and parental consent may be requested (as opposed to required).