Father's Will Advise

My father wants to write a Will. He has 1 son (myself) and 2 daughters (US citizens living there). My father owns the house and 10 years back we constructed the first floor (financed by me) and my father made a gift deed of the first floor in my name. We have two kathas now (ground floor in my father’s name and first floor in my name). I live with my wife, daughter (first floor) and parents in (ground floor). My father wants to write a Will such that I pay X lakhs to each of my sisters and the entire house will be transferred to my name. And this is after his and my mother’s demise. My question: 1. Is such a Will possible to make (paying X lakhs to sisters) and if yes, how can it be executed. Will I require a NOC from my sisters after my parent’s demise? 2. What other conditions need to be included just for my idea. For example if sisters or myself are unable to execute Will or sign, will it go to the next generation, etc.