Absolutely! Those cards work just like credit cards, though there is one simple thing that needs to be done in order to successfully make a Vegas World purchase with one.
When using a pre-paid gift card, it's essential you select the "This is a prepaid card" check box on the Payment form. You will find it on the Payment Form page below "Name on the Card" and above "Security Code" on the page where you provide the card info (name, address, card number, etc.)
If the "This is a prepaid card" button is not checked, a transaction using such a card will most likely fail.