Thanks for your info.
I called the airline agency and it seems not a good idea to modify the flight intinerary. So the best solution for me might be getting insurance. The crusie.com where I booked the cruise quoted $177 for 3 people. Wonder if there are any other places with better rates.
With the insurance, if we miss the embarkation, does the insurance company make arrangement to send us to the next stop an cover the whole expense?