If you want to get the full flavor of New Zealand then I would suggest the Moa Trek 23 day Kakapo Tour. Moa Trek is a family company that concentrates solely on New Zealand tours so they know it inside out. Our guide, Andre was the ultimate guide. He was so knowledgeable about most aspects of New Zealand whether it be; history, business, agriculture, wine, food or activities.
The Kakapo is a activity filled tour but you can find more thrills through their optional activities supplement. If you are new to New Zealand and you want to see both islands in one tour I would suggest this one. If you have your heart set on Stuart Island, I would add a few days on the end to explore it.