There are BDM records at the Fiji National Archives for your ancestors. I spend time there when I can researching my own family lines, and keep an eye out for names I am familiar with.
Most of the records you are seeking will be found in the Fiji Archives and Methodist Church Archives (also kept at the Fiji Archives building. you will need permission from the Methodist Church however to view these).
As a matter of interest, please be informed that MANY of the records kept at the LDS site are mostly IN-ACCURATE.