Can anyone explain why Orbitz has availability for our dates, but Disney reservations does not?
It can be confusing. Orbitz is both an online
travel agency (OTA) and a travel wholesaler.
With "normal" non-wholesale hotels, when you search for a room on an OTA, that company pulls from the same database as the hotel chain. As an example, let's there's only one room left at the a random Hilton. Imagine one person searching on the Hilton website and another for the same date on an OTA like Orbitz. Whoever grabs that room first will get to confirm the reservation.
As
rwdavis2 suggests, wholesalers will buy large blocks of rooms at a discount price. They then turn around and sell those rooms at whatever rate they decide (within reason, based on the contract). These blocks of rooms are only available though the wholesale company. That's why Orbitz might have a room when Disney does not.
In days of yore before the internet, travel agencies sometimes banded together to form a consortium that would buy blocks of rooms via wholesale contracts. Additionally, airlines would buy wholesale rooms and package them together with flights. Finally, specialty travel companies would buy both wholesale hotel rooms and wholesale seats on flights to sell to leisure travelers. (Examples: Pleasant Hawaiian Holidays, Apple Vacations)
Today, wholesalers are just a tiny fraction of the travel market thanks to the internet.
Cs it okay to go with Orbitz? Pros, cons?
As someone who worked in hotels and the travel industry for a number of years, I always recommend booking directly with the provider (hotel, airline, car rental) whenever possible. The reasoning behind that is because if you need to make any change, you must make it through the OTA. And although I'm certain OTAs do have some decent employees, you're adding an additional person between you and the hotel/airline/car rental person.
That said, there are times when it makes sense to book with an OTA. If you encounter a situation like this one where the only way to get your preferred hotel is through a site like Orbitz, go ahead. Additionally, there are times when OTAs have sales or bundled discounts (hotel + air) that result in significant savings. Personally, I wouldn't book an OTA to save $5...but I'd probably do it to save $25.
Do I need to be worried about getting the type of room that I reserve?
Some companies do hand out their "worst" rooms for people who book wholesale or opaque bookings (i.e. Hotwire or Priceline). Fortunately, Disney is
NOT one of those companies. You shouldn't need to worry about not getting the room you booked simply because it was through Orbitz.
TL;DR: If Orbitz is the only place selling your preferred Disney Resort, it's okay to book.