In general, if the flights are operating, BA will not change them, because they only have to get you there even if all there is to arrive to is a pile of rubble. So you're either looking for some other reason to change, or hoping they are nice to you.
Other reasons to change: Has there been any schedule change? You may be able to ask for a rerouting based on that.
Being nice: There is a clause in the conditions of carriage about cancellation if a journey is in vain; usually this is used for situations like a day-trip where the outbound is so delayed you would have no time at the destination for your business meeting, so it is clearly pointless. If there is no resort to go to and no alteratives nearby, you could argue that the trip is in vain. If you contact BA to ask about this, make sure you've got some proof the resort is gone, like some contact from the resort or a link to their web page saying they're closed, or similar. Also have an alternative itinerary ready, preferably one to a nearby island or a shorter/simpler/cheaper routing.
Do you have travel insurance that covers hotel failure? If so, contact them also - if they will cover it, go via them and let them sort it out with BA.