Wirelessly posted (BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
I would check aa.com to see if there are "MileSAAver" seats available to Hawaii on your desired dates of travel. If there are, I would try to get the sign-up bonuses for two Citi/AA cards, and hope that the MileSAAver seats are still available by the time your bonus miles post.
By the way, why do you want to spend all your time on Oahu? How about Kauai or Maui or the Big Island?