How do I make Chrome the default browser in the OSX Guest Account?
The crucial point to realize with the Guest account is that the User homefolder it creates, with preferences set in its /Library/Preferences folder, are wiped upon logout.

To effect changes, you need to make the changes (add the specific preference files) in the /System/Library/User Template/English.lproj folder. This folder contains the generic template User Homefolder structure used when creating a new user or the Guest User.

This page has details about how it is done in Snow Leopard, but it is applicable to Mavericks.