would they still be taken care of by a third party…your wife? you are work 9-5…who will look out of them? who will cook for them? who will make sure their basic needs are being met?
in your sisters home…she would be home with them whereas your BIL will be working til evening.
Personally…like i said…sending my parents to my brothers home would not be very comforting to me since he wouldnt be home to look after them. What if he has an evil wife or something?