Maybe meet at Plimmerton weigh station?
https://www.google.co.nz/maps/@-41.077268,174.8733981,3a,75y,359.24h,76.79t/data=!3m6!1e1!3m4!1sGtLkVoqKYb_Sm5YClvkTjQ!2e0!7i13312!8i6656!6m1!1e1
Google says it takes 27 minutes from there and it starts at 9 so maybe meet there at 8.30 to leave slightly after that?