Correct that Rewards dollars can be used to pay towards a cruise or park tickets (or WDW resort, dining, shopping,
DCL onboard expenses, etc.).
update: No more expiration dates on the Redemption cards. Chase (or Disney) changed that last year. Rewards held on your account still expire (I think it's 5 years after earned) but once transferred to the Redemption Card they don't expire.
Enjoy your cruise!