RichC, I also have booked for 2 people $100 each for the future cruise credit program. I have discussed with both the future cruise consultant and recently with the Captains Circle if it is necessary for pay for two people. They have confirmed that the deposit is per person and per cruise segment. If you only pay $100 you will only receive the shipboard credit for one person and the reduced deposit for one person. Also, if you like to do back to back cruises like I do, you need to pay $100 per person per cruise segment so for a couple booking two cruises back to back that would be a $400 deposit.
Hope this helps. Joyceh