sale of my father's self acquired property (my father is still alive)

My father is selling his self acquired property and he has also taken token advance from prospective buyer towards this & It is expected to take around 3 months to complete the sale transaction. Since my father is very old & sick, is it advisable to obtain power of attorney on me & my brother's name to execute the sale of property in the unfortunate event of his demise & to avoid any dispute from my sister (married). We also have 1 married sister, however, my father has decided to gift the money out of this ale to me & my brother.