Auckland Zoo is a good size, with a wide range of animals to see. It opens 9:30am - 5:30pm all through the year, but closes at 5:00pm during the winter months. There are plenty of opportunities to see animals and birds being fed, and there is a set time table for this - the first feed is at 9:45 am, so it's best to check the table as soon as you get there, so you don't miss out.
The animals are divided into sections - you can go to the Penguin Shore, which involves going into a tunnel to view the penguins swimming around, and to the Pridelands, where you can see giraffes, lions, ostrich, white rhino, and zebras. Hippo River is good, and we saw them wallowing in their mud pools. There is also a Rainforest area, where you can see masses of monkeys, and a tarantula for the braver people!
The best part for me was going to the Kiwi and Tuatara House, where they keep the two endangered native species of New Zealand. It's dark and quiet there - just how the creatures like it! And, I spent ages watching the kiwis snuffling around the ground - very cute! And, as with all zoos, there is the inevitable souvenier shop (at least get a postcard picture of a kiwi, as you can't take them in the house), and a cafe, which sells good food, and is pretty reasonable, too.