Even if you booked with DU I would contact the Dolphin to make sure they had your reservfations. When we checked into the Swan last week, there was a guy standing next to me that had all his documentation from DU, but the Swan did not show a reservation. He was on the phone with DU trying to get a room at another hotel. If I'm not mistaken they could only find a hotel off-site. However, I did hear him say that DU did get him in the Swan on the following day.
Better safe than sorry.