No charge will be made to your credit card on file until you hit a resort threshold ($2500 for deluxe and $1500 for mods and values - maybe it's $2500 for mods as well), or until about 2am of the morning you will be checking out.
Until that point, anything charged to your room via your MB is just a debit on your account. You can pay on your account at any time with cash, giftcard or credit card. To avoid an inadvertent charge to your credit card, just stop by the front desk every couple of days, ask for a print out of your bill (so you can check for accuracy - mistakes do happen) and then use the gift card(s) to pay the bill. It's pretty easy and doesn't take much time.
Steve