Most garages do not have a moisture barrier installed below the conrete. This will pose a problem for any type of adhered flooring system.
For the type of use you are proposing, I would recommend looking into polishing the existing concrete floor or applying an epoxy floor finish.
For more information:
Read "Is concrete flooring eco-friendly? What's the best way to finish it-stain, paint, polish?" a Q&A answered by Brad Hubbell.