The emergency evacuation of a cruise liner has been a concern for many years because of the numbers involved - as we have seen, even with 5 helicopters it takes a long while. We had a similar situation off Holyhead many years ago using the 2 SAR Wessex from 22 Sqn plus the SARTU fleet.
Deconfliction between the air assets is easy, just use a common frequency and have an on-scene commander directing where to winch from - fortunately a big deck like a cruise liner offers several simultaneous winching positions - as long as the ship's crew know what they are doing when corralling the pax into the right places.
As someone has already mentioned, the real problems occur when you don't have 5 or 6 winch-equipped helicopters immediately available and fuel is not readily available.
We used to be concerned down in the Falklands when the big cruise liners appeared, doubling the population of the Islands as each ship arrived - one SAR helo with the possibility of a second plus some old S-61s without winches fitted.......Not sure it is that much better there now with a 189 replacing the Sea King and the same older S-61s.