You can also rent directly from Sheraton. It's probably cheaper to rent from an owner for a full week. DH and I will rent a 1 BR directly from Sheraton for a long week; we earn loyalty points which we use at the Swan/Dolphin for free nights.
Remember, there are two Orlando-based Sheraton Vistanas and you'll have to know which one you want. Either the Sheraton Vistana Resort or the Sheraton Vistana Villages.
I will note that when I say "closer", its only closer by a smidge, as really the two resorts aren't very far from each other.
The Resort is larger, while the Villages is newer. The Resort is currently rated 39th out of all properties in Orlando on TripAdvisor, while the Villages is 70-something.
The Villages had a pirate-themed pool area that small kids might enjoy.
I've been to both. The VV resort is larger and older, in my opinion, too large. The villages is newer and a little nicer. They are both nice but not as nice as the Hiltons or Marriotts IMHO.