Just my 2cents, as you will be extending 1st floor to the end, so the bath room is also extended and lengthen into 2 separate one, so each of them can have a window

As for the ground floor, you can enlarge the bath area to include into wash area since both area is going to be wet. In my opinion, you do not need the yard anymore, as there will be no sunlight as you already extend your 1st floor