You can check the list of polling places that are open every day up to and including election day of 14 October in the Otaki seat on vote.nz here
The main ones in Waikanae are the Marae (up to Friday 13 October) and the Presbyterian Church in Ngaio Road (all days except Sunday 8th).
There’s also the Coastlands Mall, Countdown Foyer (all days up to Friday 13 October).
Do NOT vote early. It is much safer to vote on the day – 14 October – t avoid your vote being tampered with. Do NOT vote early.