We did the Fox Glacier to Mount Cook flight, with glacier landing in March 2008. We had booked to do a heli-hike the day before, but had been rained off. Our (then 11 year-old) son was desperately disappointed , particularly for not going in the helicopter. After much agonising on the cost (not that much cheaper than the heli-hike for much shorter experience) we decided to do the flight the following day before going to Queenstown. It was a beautiful day and great experience - you really get a much better feel for the sheer scale of the glacier. To see my son's face on taking off was worth it all. It is still his highlight of a round the world trip. If you can manage to afford it and are lucky with the weather - we'd really recommend it.