>>5603012I've done hiking in the south and north island.
For the south island, you might want to try walks in Abel Tasman or Fiordland, do the routeburn
For the North island there's the coromandel and bay of islands
For summer stuff you could try jet boating, bungee jumping, and other similar activities in the south island, or swimming in the north island, there are some good beaches here
I'd suggest looking up tourism websites tbqh