our fingerprint taken already

Yes, We take our fingerprint last Nov, recently, we received letters from USCIS, asking my kids to take fingerprints. My attonney said it is clear mistakes and just ignore it. I called USCIS, that lady told us it is just take a pic, may not for fingerprint. But for I-485, need to take a photo for kids?

Our case, NIW, California center,
I-140 submitted Sept 2003, Approved Sept 2004,
I-485 submitted Oct 2004.