Air New Zealand’s drop in regional prices means that its a good time to book travel for Phoenix. To repeat last year’s advice: if you are flying in from the North Island, I would recommend an arrival time no later than 16:00 so you can coordinate with other travelers for transport. We’re arriving at ~13:00. Saga normally organises car-pooling, with a group leaving from the airport, so you may not need to hire a vehicle.
For return, organise departure time of 18:30 or later. Earlier may involve stress, and possibly having to skip the last round.
At time of posting, you can get there from Wellington with a big bag of costumes for ~$170 ($104 there, $54 back, plus credit card fees and carbon offset). Its a similar price from Palmerston North. Flights are cheaper if you arrive earlier in the day, but flights home are cheap - I guess no-one wants to leave Christchurch on a Sunday night.