Hi Grant & Carol,
Carol, you will find me on the island I'm sure. I will look for you and the kid.
Grant, the cabana place I recommend the most is Mara's. Its right next to Tinas Hostel and in a very good location. Its located next to the split and the only beach area on the island. Very interesting part of town. It also has a dock out front for some bone fishing or the split for some small snappers. Price is good too at $30 usd approx or less and very clean & comfortable.
You should try and call Mara at 501-22-2156 as she is popular and usually full. Otherwise, I recommend seaside cabanas (more expensive) at www.seasidecabanas.com
or Ignacio huts (rustic & cheap) about $15 usd on the South end of the island. A bit of a walk to the main spots though.