US Immigration from Kazakhstan

Hello,

One of my relatives was selected for DV 2022 and the only issue we are concerned about her and her family is their marriage certificate and child's birth certificate. The couple was married a few years back and they have a toddler, however they never applied for marriage certificate and child birth certificate. They had wedding and everything but no legal documents to this day. When they filled their dv-2022 application they had registered themselves as married couple. Now, the question is, if they will go ahead and receive their marriage and child's birth certificates, would this have a negative impact on qualifying to their visas as a married couple or it is not going to affect in any way during interview? If it won't effect negatively then is there a chance the KCC/embassy may ask for parental blood test results for the child and/or affidavits from relatives confirming their marriage is genuine? Please kindly share/advise if anyone has a knowledge/experience about this kind of situation. FYI, DS-260 hasn't submitted yet. Thank you!