How about a compromise....
I see you all have a little more than three months until your cruise. I applaud you for considering a suitable punishment - hopefully one that will fit the crime.
Why not give your child the option to 'earn back' the right to go on the cruise? Depending on the age, there are plenty of options available from helping with large, not-so-fun chores around the house (cheap labor is good for embarking on a nice new landscape for the yard.
) to helping out neighbors. If the person in question is old enough, perhaps helping out the community via charitable work is in order.
Whatever you do, spell out the terms (in writing is good) with a clear deadline AND the reward for completing (in this case, going on the cruise) or the consequence for not following through. Whatever the consequence, make sure it is something you can live with.
My $0.02, its not right to punish the rest of the family, and it's not right to leave him/her behind either. But that doesn't mean that the sanctions have to disappear once you go on the cruise. Perhaps a book list of required reading to be completed while on board is an option. Meaning, he/she still gets to spend quality time with the family, but will be so busy reading that there won't be time to socialize all over the ship, i.e. having "too much fun" like what would have been had he/she not committed the original offense to start this discussion.
Did what I say make sense?