請教小白兔 Xiao Baitu- Signature for kids

Hi Xiao Baitu, I filled out the I485 for my 8 year old son. I signed my name in the place of “Signature of person preparing form” and my son signed his name in the“Applicant”signature place. Is this correct? Or should I sign both places for my son? In addition, the G-325A (Biographic Information) form has no “Signature of person preparing form” place. Who should sign his name in the signature for “Applicant”place, me or my son? 謝謝.