You may want to try winging it. There are a lot of nice places to stay within your parameters.
Consider Exotic Caye too, good lively bar and pool.
a couple doors down from Coconuts, another lively spot. They are all on the "Lodging"link on this page.
There is a detailed map on the Lodging locations via the "Home" link at the top of this page too.
Click on the "Maps" link on that page then "Big list of maps".
You'll have a great time!