I've tried to resist posting this, but I must. Just a couple brief points with all due respect:
1) There's really no reason to reduce your credit limit for fear your card will be stolen. It won't reduce your liability, which amounts to 50 bucks pretty much no matter what. I carry very high limit cards which have been used fraudulenty and I've never paid anything.
2) If you're financing the cruise through a credit card (or transferring other credit card balances to a new card), I'd think real hard about whether you should drink champagne every night or apply the price of the bubbly to your card payment to lower the balance and pay a little less interest.
Credit card interest is usurious, and 5000 points doesn't begin to make up for the excessive interest charges you'll pay over those two years.
There's only one way to beat the credit cards: take their perks AND pay your balance in full every month. Without fail. If you do it any other way, frankly you lose bigtime. Because short of the guy from Jersey in the pinstripe suit and wide-brimmed hat, in the long run they're about the highest-priced loan you can float.
And in some ways they have to be. After all, somebody's got to pay for those of us who use the credit company's money and never pay a cent to do it. Ever. The only acceptable interest rate is zero. And not for six months. For always.
Again, my apologies. Don't mean to preach. I've simply seen so many people get hurt by this.