WE purchased ours from a discount coupon off the web. Actually, I called Marriott to book it and asked the difference of booking with them or thru this discounted tour place and their reply was just the price. We had to pick our tickets up and pay cash for them, but we rented a car, so that wasn't a big deal.
Other than it rained on us, it was a nice time. Email me if you have any other questions.