1.they are hiding identity for obvious reasons, fear of getting into trouble because of that much amount of hard cash,your one complaint with their identity & they will be behind the bar or at least under the radar of government agencies
2.talking about the ease of your decision making,if you desperately want that money as your respected father has debt to be cleared,you shouldn’t mind accepting the deal strictly at a higher price,by leasing him out the land for 99 years with a one time on paper deposit
3.the hard cash can be utilised in various ways to clear the debt,I can help you to source it into white amount,it’s totally your choice as it’s possible,instead of sale deed you can consider leasing it out for 99 years,later on let him claim the land and you shouldn’t oppose it