Is there any way the call could be moved ahead...or wait until you get back?
Unless you've got a specific time and day organized for the call, I can't think you're going to be all that relaxed on your trip waiting for the phone to ring.
The cell service could be booming in the day of - full bars, crystal clear......or not. If you explain your situation, there may be some wiggle room.
(Although, "Yes, I'm going to be on a sailing yacht in the Caribbean" might not get you any sympathy)
A boat on a mooring moves as well, you're going to find the signal strength comes and goes, unless you're ashore and then you've got others to deal with as well.
Best of luck with the opportunity!