We are US nationals living in Spain on temporary residence permits (renewed every year for the past 4 years now). We have a new baby who has a Spanish birth certificate and a US passport but no official Spanish ID yet. Can we travel with her inside Schengen zone with just the two pieces of documentation we have already? We are thinking of visiting Switzerland.
Considering that your kid has a valid US passport he is entitled to the Schengen entry as well. Since you are the parents you may need your marriage certificate and the baby's birth certificate; only for them to verify that she is your kid (they want to be sure you are the legal parents/guardians).
As long as she is a US passport holder (passport valid for 6 months) she won't be denied entry.
As a reference you can read this:
But if she has been in Spain for more than 90 days and doesn't have any Spain resident documentation i.e. on the passport, a resident card etc then you should wait for it. The reason is she may asked to leave the Schengen area and enter it again which may pose a problem for you.
If she isn't 90 days old yet then there would be no issue.
I was a in the Schengen area as a tourist and was offered employment in the Netherlands within my 6-month stay. So during my work stay I wanted to go for a weeks vacation (while my employer applied for a visa conversion). I was told at the Netherlands exit immigration that I wont be allowed to travel within the Schengen area after 1 week (because the 6 months were coming to an end) and I would need to exit unless I have a resident visa of any Schengen country.