What's the best place to go in 3 days in South Island?

What's the best place to go in 3 days in South Island?

My family is travelling to New Zealand on 2nd week of March for just 5 days, including the flights in & out of NZ. We are going for a short visit to a relative. My daughters are ages 9 & 11 yrs old. What do you suggest we can do with our limited time?

Question about Drive New Zealand's South Island