You can do option 1, and take the ferry, but either way, I would take the ferry as it's a great attraction in its own right. Great views through the Marlborough Sounds.
The only problem with 1 is the time it would take to do this. Also, there's little to see in Christchurch itself, but you could see Akaroa, about 90 mins south, which is a gorgeous town, then Mt Cook and across to Queenstown, then the Haast pass and along to the West Coast Glaciers and finally up across the top to Picton and the ferry. This can be done in 2 weeks, but does include some big drives. Also, in Queenstown you'll probably want to see Milford Sound which is either a 12 hour round trip (including 2 hour boat tour) or, a 2- 3 day event with overnight stops at Te Anau there, back, or both.
If you do 2 you cut out one side of the south Island - you see Queenstown, Milford and then either the west coast glaciers, or Mt Cook, the Christchurch region, Kaikoura and up to Picton.
On the north island Wellington is worth a day or two, then up to Rotorua and Auckland. A 2 week south/1 week north split is usually about right.