I used the following wording for my invitations:
Together with their parents
ME
And
HIM
Request the pleasure of your company
Aboard their wedding cruise
On Princess Cruise Line's Ruby Princess
Departing on Saturday, the ninth of January
Two thousand and ten
From Fort Lauderdale, Florida, USA
Ceremony to take place
Tuesday, the twelfth of January
At Bluebeard’s Beach
On the island of St. Thomas, USVI
Because I used a pocket fold invite, I'll look to include a note that an invitation to our AHR will follow. Unfortunately we are unable to plan our AHR until after our cruise as my FI is in the military and we're not certain as to when he will be available (it was a big struggle for us to be able to secure our wedding date because of their scheduling).