3 to 7 days on a cruise ship sounds like a dream, especially when compared to the experiences of being in the navy I have had. where it was 30 or so days, with no amenities, just work work work. but I an derailing the thread with my random wailing, and that is not kosher, so go for the 7 day one, and take 5 days off and 2 to party.
Damn the vacation time thing, whats the worst they can do, fire you?
Edited to add: Oh, and on the subject of the navy, if you want a cheap cruise and know someone in the navy and they are out to sea, you could always hope their ship will have a tiger cruise(dependants cruise, you can lie) from Hwaii to San Diego. Would lower the costs greatly, and you could sit around and do nothing but watch the ocean go by for a few days. The lack of amenities blows though, but if you like military stuff, could be a real kick in the pants.