Heirship certificate and executing the property documents

Owners (husband & wife) of the property (flat in cooperative housing society in Navi Mumbai) dead in 2008. Deceased got one son and one daughter. They obtained heir ship certificate from competent court. However, they have not changed the name of the ownership to them in any of the property records, i.e. CIDCO, Revenue records, Society records etc till now. All the records are still in the joint name of the deceased. If someone wants to purchase this property, any need to change the ownership first to the legal heirs (son & daughter) and execute the agreement of sale between the joint holder (son & daughter) and the purchaser? Alternatively, if the name of the property is not changed (i.e. still in the name of the deceased), whether the legal heirs can sign on the behalf of deceased in the agreement of sale where all the details including the death of the owners as well as obtention of heirship certificate etc are brought out? Whether Registrar will allow this? Please enlighten me in this matter.