Sorry, I don't know all the individual prices but I just booked 2 adults and 3 kids rtn to Christchurch during jul school holidays for $800 return. It's a very cheap family sking trip!
Mt Hutt/Potters ski fields have kids under 10 ski, stay, travel free. Ski lifts prices are way cheaper than Oz and accommodation is plenty and cheap too. Free shuttle transfers to mountain from car park base if you don't want to use chains.
Travel validity is 3 april to 12 December!!!
Looking at goin over the week before June/July holidays, and skiing with a mate.
Air NZ also has $150 all return flights til the 14th so will have to do some research.