Was your son making backups of his 5s to either your computer (using iTunes) or to iCloud? If he made a recent backup, all his data can be restored to the new iPhone. If no backups were made, the best suggestion I can give you is to try and guess when the passcode question comes up on the screen, try typing it in. Normally, when the phone first comes on, it will ask to slide across the screen, and that's when the passcode question comes up. If you can't slide across the screen because it's cracked, you may be out of luck recovering the data without a backup.