I would book a cruise using AARP discount cards if they are available for your cruise line.

Royal Caribbean, HAL, Celebrity and Carnival give 10%. Princess gives 8%.

For our mini-suite for the Discovery Princess Eclipse cruise we spent about $3k on the cabins, plus we put some money into an onboard credit using gift cards.

Amex would have only given us $200 so we came out ahead.

HAL and RCL give 10% so that is an even better deal.