As already mentioned, there is so much to do outside of the parks that there is a possibility you may not do a park every day. I tried the resort hopping once with a friend, he is now my husband, we had that much fun that day. Downtown Disney and Disney Marketplace are a day's worth of activities too, shopping and free entertainment galore, and the restaurants are world-class.
Are you a Florida resident? If you can upgrade to a 10 day pass, then maybe consider an additional Florida resident three day or four day pass to round out the 12 days. Don't forget that you have six months to use it from the first use. I still recommend the Water Parks and More options, because you have six months to use them.
Resort hopping doesn't cost anything and you get to check out all of the modes of transportation and see the property. I read on one of the boards that you may kindly request a transportation card from any driver and they may elect to give you a collectors card, I don't know if they still do it, but here is the link to that discussion.
http://forums.wdwmagic.com/showthread.php?t=579660