Going to Christchurch next week?

Hey guys. My parents and I are heading over to nz for 7 days (6 really) for a short holiday. It was only meant to be a quick 3 day weekend in ChCh but now It's a little bit longer so we thought we'd cram as much in as we could!!!

We arrive in Christchurch late on Tuesday night so we have all of Wednesday in ChCh. What is there to do?

So far I have: 1. That Antartic centre place
2. Have a quick look around the city (at the cathedral etc.)
3. Take a drive over to Lyttelton.

Anything else to do in Christchurch? We aren't really after too much, just to have a quick day in the city and get a general feel for it :)

The next day we're heading down to Queenstown. How far is that from Chch? About 6-7 hours?

And how far is Invercargill from Queenstown and then Invercargill back to Christchurch?

I know it sounds like a lot to pack into one week but we will manage haha.

Any ideas on what to do?

Thanks in advance :)

Edit: Oh and also the night we arrive in Christchurch we're actually sleeping in a camper van lol. Were are some safe places to sleep like a caravan park or something? Cuz I know here on the Gold Coast people always get attacked in them. Where is safe to stay in Chch? Any ideas?
Additional Details
We're not really going to Invercargill for 'fun' per say. More as a joke lol (no offence residents of Invercargill). And possibly Bluff. IS there actually anything to do in Invercargill haha.