Full-heartedly agree with the Helo. A helipad (LZ) is easy to create - trained EMS/FD do this all the time and in a place like Ambergris Caye is would be easy to define accessible areas - pre-defined LZs if you will - in an EMS plan.
However, there is still the necessity to stabilize the patient, transport same from the scene to the LZ, and ensure they are ready for the flight. Please do not discount the value added added to EM services. In my view, they are a priori service to any medical system.
As for the budgeting...tough call. A tax on visitors? A tax through businesses? Voluntary donations? I have lived in places where one or more of these have been in effect.