hi vikas,
congrats for your MR, i too have the same problem as you, i too from india , chennai, my wife and i applied for pr we are having 3 months old child with us, we actually waiting for our medicals ,i too going to add my son in the applicant, i don't think POF is required for him, what u required is passport size photographs with mat finish six numbers, family photo, DOB certificate, pass port. and visa fee is required as per my knowledge, inform vo through a mail about ur new family member, apply for tatkal passport which take take hardly 15 days max iam going to do that, any way all the best vikas for ur visa n ur kid