best option in my opinion would be to arrive at santo domingo instead(may be too late if already booked) and drive or hire a taxi or to fly there.
Home this company does flights from punta cana to portillo airport which is a short taxi to las terrenas. they only fly monday,wednesday and friday but they may do a charter flight but am not sure of the cost. i do not think the ferry is reachable in that time frame. good luck,,, ben ( to get more answers you may wish to start your own thread so people do not get confused on the thread tiltle... just a suggestion

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