Same here, but we didn’t notarized Imm5604 form.Yes, my situation is same as yours. Myself and my wife is a PR but my son born In India. Now my wife is in India with my son.I didn't add her as a co-signer . Also Included the notarized imm5604 form along with an explanation letter.
It is a declaration from non accompanying parent which is not necessary in our case.