Waiheke Island Viewing Point is a lookout in Maraetai 2018, rated 5.0 from 7 Google reviews. One reviewer mentions the view and the walks, and another mentions easy access to the beach.
A good lookout is judged on its view and on how easy it is to reach, since a short walk or simple parking makes a real difference. Coastal lookouts often show the water and islands most clearly in clear light or near the turn of the tide. Check the path and railings before taking children up to the edge, as these vary a lot between lookouts. Regulars usually bring a layer, because it is often windier at the top than down by the shore.
For a view across the water from Maraetai, this lookout is worth a stop.