We combined both the CC coupon for The Century in January & the upgrade shen we first booked a few months ago. We ended up getting a better deal when rates dropped( cat 10 to a cat 4 for several hundred dollars less), and they still discounted that rate too.
I spoke to Celebrity today and they told me you could use both. I told them I had already deposited for my August cruse for two cabins on captains club member in each and they told me they would apply the coupon to each room for a total of $250.00. I have also been given the upgrade on the Mercury from a 3 to a 2 which is an outside to a balcony. An additional saaaaavings of $800.00
I have mailed them the coupon....lets wait and see what happens.