Twardzik's here for another season too.
I'd keep Kerr, McDonald, Sutton and (controversial) Law. I'd like to see Kerr have a full season at centre-back, he can clearly play when he's in his preferred position and is certainly no worse than McManus, Laing and O'Brien. McDonald will score goals for fun once he is settled as will Sutton with two natural wingers (Thomas and Johnson) in the team. Law looked hopeless under McCall but has somehow managed to turn his season around and looks a competent right back, so same as Kerr - play him in the right position.