As far as the Finder window.. that's the name of the Home Folder and that can't be changed.... BUT you can just make a new user and go from there... after the new user has been working for a week or 2 with no bugs or issues... delete your sons user account. This is all done under System Preferences/Accounts.
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http://davidbearphotography.com/
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It appears that autocorrect has become my worst enema.
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