your question is hard to understand (rambling), but if your reservation was not a pre-paid, then the CC is only used to guarantee the reservation and is not charged until you checkout, however with a GC you use the GC for the actual payment (and the CC is not charged).
Yes, you can use multiple GCs if you have insufficient in the first card the remainder can be charged from the second............
Originally Posted by
javabean
I see there are some good gift card promos, I never used a hotel gift card before and I'm new to Marriott too.
So I just buy a gift card and use it at check-in or check-out to pay for my stay, right? The reservation says "Your reservation is guaranteed to your MasterCard". It means they are not going to charge my credit card before check-in, correct? I've seen hotels doing that even though the resevervation said no pre-pay. I actually was surprised the hotel did not require anything pre-paid on a promo rate. It's actually a Renaissance. If they charge my credit card, I would not be able to use my gift card(s). Then I would have $1.5k worth of gift cards unused

Unless they refund the credit card.
Also, can I use multiple giftcards to pay for one stay?