As it turns out...

...you need to bring birth certificates for any child under the age of 16 with you to the passport office when you are applying for a new passport.  You must do this even if you have their original passport with you!  We also discovered the hard way that both parents must be present when applying for a new passport, along with their government issued photo IDs. 

So this is how the day went... we drove with excitement to the passport office at the university.  (Kids were singing and joking in the car.) We stood in line for our number. When called, we proudly presented our old passports and announced that we'd like to renew!  

The workers at the passport office politely turned us down and sent us home for both birth certificates and the father.  

We drove home in frustration (and total silence).  We found the certificates, rallied their dad... and an hour later, we showed back up at the passport office - in a much less excited mood - and continued to fill out four identical forms, stand in line again, take photos sitting in a chair lined with a white sheet, and write checks for nearly $500 to get the renewed passports. 

It cost $80 for each child passport renewal and $110 for the adult passport renewal.  There was also a $120+ university processing fee.  If we'd wanted to expedite things we could have paid an extra $60 per application.  Yowza!  It ain't cheap to prove you are an American citizen abroad.  I wondered if the cost and complication of the process ends up stopping many Americans from applying for their passports?

In the end though, we left relieved and heartened by the news that in 4-6 weeks our new passports will arrive by mail.  The passport photos of the kids were also pretty precious.