Generally I would think they wouldn't have anything available. It's a fairly popular restaurant just in and of itself, never mind the fact that it's attached to the DLR.
You can try to make an ADR, and if that fails, they might be taking Walk Ups at the door.
We had a choice of 5, 5:30 and 8:30, since the parks close at 8, we chose 8:30. We'll have 45 minutes to change and all that jazz. Perfect! Thanks guys.