I say look for a used road bike, I rode a mtn bike with the knobby tires and it was HELL! I was the only fool out of 350 on mtn bike. The day after the race I threw the new mtn bike on ebay and found a used specialized and Im so much happier and its way easier to ride. I highly recommend clips and shoes, screw all the toe clips. and i wouldnt think the aerobars would be that big of a deal in a 12 mile ride, yea if you were doing a Olympic tri or IM or HIM then they might be more benificial but for such a short distance i wouldnt think they would help much