Also consider Phu Quoc. its got a good beach (not sure about 5* resorts, a few were proposed and going to be built when I was there in 2012/13) but there are quiet decent beachfron hotels/resorts still. Up until a few years ago, there was no cars on the island, its changed a bit now (ie going to be full of tourists in a few years time) the airport is massive and brand new and way oversized for i think 3 or 4 flights a day it recieves? so the planning is there. the town itself it a typical vietnam town, nothing overly exciting about the town area itself. good food markets (seafood). And a fair mix of restrauants along the main road where the resorts are. Again we just hired scooters are rode around alot of the island away from the beach is rainforest type. a few quiet private beaches around if you go for a drive. Good boat trips for snorkling ect, and seeing other islands. Think they also run fishing charters if your into that