Not to honk Priceline *too* much, but for New York City you can bid on *very* specific zones within Manhattan.

Bed type is rarely guaranteed through any of the booking methods. Even booking straight through Hilton.com or Marriott.com, you are indicating preferences, but the hotel isn't contractually obligated to give you that bed type. (In most cases anyway - I hear Marriott is rolling out firmer guarantees to its elite members.) Fortunately, over Thanksgiving the hotels will probably be emptier than usual, so you shouldn't have trouble getting two beds.