M.S.
Why prep food a week ahead when it only takes moments when you want to eat it? They will go bad and will loose some nutrients. The only thing I would do ahead of time might be slice up banana's and freeze them (they are really good this way). Otherwise, how long does it take to core and slice an apple? Peel a banana? Wash up some strawberries? You are better off, leaving the fruit in it's original form, and letting your toddler choose between two, do you want an apple or a pear? Then cut it up or hand it to him, depending on his age.
Good for you for wanting to feed him healthy snacks!
M.