Bring lots of books, but remember that you’ll also want to watch beach TV. Reliable channels include Waves, Clouds, Dogs, and Children. Sometimes you can get Horses or Storms; occasionally Sparklers.
Someone’s going to be Beach-Fire-Building Alpha. If that’s not you, assist them by gathering kindling, carrying foodstuffs to be carbonized, and not complaining when smoke drifts your way. If you’re the Beach-Fire-Building Alpha, rule benevolently, and gracefully accept all praise of your skills.
Consider not taking sunset photos because geez, aren’t there enough of them in the world already?