Bangalore BDA property Sale without Absolute Sale Deed

1981 - Property Alloted to Father. 1983 - Possession Certificate issued. 1984 - BDA Condition Deed of Sale executed on 1984. BDA Conditional Deed of Sale, Alloment letter, Possession Certificate, BDA issued Khata. are all the documents available. 1988 House Built. Loan applied with existing papers. 2000 Upstairs house built with another loan applied with existing papers. 2015 All loans cleared and Bank NOC received. 2020 BBMP has issued Khata Certificate with property Id assigned reaffirming ownership etc. 2023 Father passed away. No gift deed done. Nor is there any Absolute Deed. Buyer is ready but is asking for Absolute Sale deed to be done in the legal heirs (Son and daughter) name. The cost is on the current guidance value which is enormous. Should we procure the Absolute Deed in the father's name and register it? Wont it be a waste to spend money registering in the father's name or the children name when it will again be immediately registered in the buyer's name spending the same amount? What would be the best legally viable option without having to spend the money twice?