What a fabulous idea. I might phone my 7 year old nephew as my children are too young to play.
You could do the identity one about the broom - if you replace the head, and then later on replace the handle, is it still the same broom and if not when did it stop being the same?
Ethics - how do we know the difference between right and wrong?
Is it better to be a happy pig or a miserable intelligent person?
How do we know we're really here and not just dreaming?
(or as some ancient Chinese guy put it - Last night I dreamed I was a butterfly. How do I know I am really a man who dreamed he was a butterfly and not a butterfly dreaming he is a man?)