Dara:
I'm not AskTracy, but I'll take a stab at your question(s).
It's just like when you check into a resort at WDW and use your KTTW key for charging. You give them the charge card that you want to use and that's what they assign to the KTTW. You can't charge things with anything else other than your KTTW onboard or on
Castaway Cay. So, if you want to use a Disney VISA (for example), that's the card you assign to your KTTW. Another example is that we'll probably assign our debit card to the KTTW and I am making prepayments to the shipboard account every couple of weeks now that my cruise is paid off.
I assume if you have a gift card or rewards card, you present that and have the balance added to your onboard account, just like the Dreams credit is. That means that any charges you make will first come out of the Dreams credit and that gift card amount, before rolling to your credit card.
Make sense?
It's actually a very convenient system, but I recommend checking your balance a couple of times as you go. It's really easy to just keep using your KTTW for drinks and such and be quite surprised by the bill amount at the end!