Elderly celebs to play Mr.Rogers and Mrs.Rogers in "And then there were none"?

I need to pretend to make a movie on the book "And then there were none" by Agatha Christie...I need people for all the characters except Wargrave, Marston and Blore. I especially need help with some actors and actresses that could play an elderly couple who serve as the maid and butler in the story. Any ideas?? I also need ideas for a young pretty girl who worked as a nanny, an old lady who is a very strict Christian, A retired army man and a doctor. And help is awesome! thanks!