Each helicopter has a crew of 4 on the boat and 4 on the shore. They hook 4 chains to the 4 corner hoists of each container. Say it takes 1 minutes per container to affix the chains, 1 minute to fly to the sand, 1 minute to unhitch, and 1 minute to fly back. Thats a lot slower than agricultural helicopters, but nobody will be very practiced with this yet, so it'll be slower.
The entire ship could be unloaded with this method in 5.5 days. Perhaps less if not all the cargo needs unloading.
The job could be half done by now...
It takes a purpose built crane a few minutes to unload a container, so I sort of doubt a helicopter could make it happen faster.
Although I suspect you don't want to repeat that trick too many times without serious inspection/maintenance.