Marisol on the pier. Bubba Gump has chased away most of the seafood, there's The Lobster, it's expensive, but take a look. The original Hot Dog on a Stick is also just off the pier.
If you go north from the pier through Malibu, Reel Inn, Neptune's Net, or higher end, but Gladstone's for seafood. Also, Duke's and several places at Malibu Country Mart, which is across the street from Malibu Lagoon.
If you'll be near The Grove or La Brea Tar Pits, there's Farmer's Market. Lots of stuff there, but my favorite since I was very young was Tusquellas, which is seafood.
And don't forget In n Out.