I'm amazed all the Mainlanders haven't bombarded you with direction on how to drive their favourite roads!
If you drove non-stop you'd make it to Bluff and back by Monday morning, if you shared the driving.
However, if you really wanted to see the country and enjoy it, I'd do this trip from Wellington :
If you went over Friday after work - say leave Wellington at 6.00 pm - you'd be in Picton at 9, Blenheim is 28kms, 30 minutes away, Kaikoura is 129 kms, 1 hour 30 from Blenheim - stay overnight either place.
Saturday - leave around 7 - it's a beautiful drive down the East Coast, you'd be in Christchurch by 10.45 from Blenheim or 9.15 from Kaikoura. stop for morning tea at the Arts Centre, go for a ride on the trams, then drive to Wanaka via Tekapo (and when you get past Tekapo get off the Tourist highway and fine the canal roads - they link most of the hydro dams and the scenery is mind-blowing. You should arrive at Wanaka around6 or 7 pm. Stay overnight.
Sunday, leave again at 7.00, drive to Haast, then head up the West coast - I'd stop at Franz Josef Glacier, it's well worth the walk up to the glacier face. You'd be arriving there around 11.00.
Keep heading North, Greymouth is 2 hours away, I forget where Shantytown is but that's worth a 2 hour stop, and there's a Morris Car Museum on the way that needs your camera.
I'd be arriving in Picton around 7 with this schedule, so I'd either take the ferry across that night and sleep in my own bed Sunday night (If I lived in The Capital) or morning ferry and pull a sickie...
Picton to Wanaka = 773km, about the same going back on the West coast, say 1500 km, three tanks full?
And yes, I'm going to keep a copy of this for myself to try one day.
Good Luck! and show us the photos!
Peter
DRGN1