Absolutely! Those cards work just like credit cards, though there is one simple step 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 Details form. You will find it on the Payment Details Form page below Billing Zip Code 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.