Usually they have quite a few cancellations so just make sure to get on the list. They also do have over flow camping but they don't let you reserve it. Its first come first serve. Ted, the head of the park has told me every year that they will take care of us and so far have. There is also the Drift Wood RV park its a little way from the river like 5 miles or so but still here in Boardman. And I know most like to camp but we do have a couple nice hotels here in town if you prefer that.
Again the best thing like Scott said get on the cancellation list soon and you should get a spot no problem.