I'm keen for a saturday lunch too,
Another accomodation option, in addition to the Pullman and Hilton would be the MGallery, which is currently being renovated to become a sofitel, not sure what dates though.
The Hilton will probably by far be the most expensive of the 3 (unless the sofitel decides a few renovations make it worth 3 times what they're currently charging.)
The Hilton location works best, the Pullman isn't too far, but it's up a hill, and the MGallery is probably about 5 minutes walk around the viaduct.
One potential advantage of the Pullman/MGallery for people with accor status is a late check out of 4 pm so if people fly out on sunday evening, it'll be better
Another cheaper option for those who are coming just for the food, and are looking to save, the Mercure Auckland (not the Mercure Auckland windsor) is about 2 minutes walk, and can be had for 100 NZD (maybe 80AUD?) a night, and they have an unofficial policy of upgrading A|Club platinum to any available suites, which could be nice.
The hilton standard rates are about 450-500NZD a night for the base room, the pullman is about $250NZD a night for the base room, and the MGallery is from $160NZD, but isn't showing pricing from beyond the 10th of Jan, so it may be related to a brand change, or it may just be not in their system.
Hopefully that gives some people a better idea of a few options there are...