Have you legally changed your name?
I haven't
Are you currently working?
Yes, I am.
In case you change your name, you should inform your employer.
Regarding the original documents that I must give, can I present an expired document with the previous name of my child?
Yes, an expired document with your child's prior name can be accepted.
Do I need anything else to prove his identity?
Yes, other documents will be needed for proof of identity.
But, I have the identity document with his name on it. Why do I need other documents?