it aint like its going to be 45km of Brokeback Beach dude.
Have you ever been to the Kapiti coast? on that 45km, is about all of 2-3 km in tiny spots that joe public and their kids use.
Rest of it is pretty isolated, and there isnt a huge amount of access points north of Waikanae. (peka peka and Te horo)
Besides, if Uncle Pervy gets down there with his ham sandwich, binoculars and vaseline, he'll get busted.
People have been rooting in the sand dunes on the Kapiti Coast for years anyhow.