New Zealand in 8 days -- what to see and do?

My family of 3, including myself, is looking at 8 days in New Zealand in the first couple weeks of July 2011. We would like to visit both the north and south island, concentrating more on the south island. We like to see cultural and city sites, but we are also nature lovers as well, wishing to spend perhaps 5 - 6 days on the south island seeing the mountains, fjords, glaciers, sounds, etc. We currently are looking at 2 nights in Auckland, 1 night in Wellington, 2 nights in Christchurch, and 3 days in Queenstown -- would this be suitable for our interests? Is this a sufficient amount of time in each city? We are looking at flying into Auckland and flying out of Queenstown. Also, what is the best way to get around? We are interested mainly in bus and train for transportation. Please advise, and thank you!