Is there any place within a few hours driving of Irvine that has a buffet right on the beach that is good? (ex. tables in the sand, like they do in Hawaii)
My guess is that such a thing might require a private beach, and there are very few of those around here. You might be better off making arrangements with a private chef or caterer to arrange something similar at a public beach. You can call around and see if the St. Regis or Ritz in Monarch Beach can prep a dinner of that type. I know the St. Regis has a restaurant that is on the sand.
dont know any buffets but if you want to be right on the sand, there's beachcomber cafe operated by rubys at crystal cove. hardly fine dining though.
the closest you'll get to being on the sand otherwise will be at some of the resorts like surf and sand, studio at the montage, or for a less ritzy but charming experience, the hotel laguna.