Auckland...what to do & where to stay?

ok so we are going to rhythm and vines for new years, and have been looking at flights etc and are now thinking of spending some time in auckland.
I've never been there, and DP's been there once.

we both like the idea of sky tower walk, the zoo, taking an adventure bus tour ($35 for the day to see some main attractions), rainbows end, and kelly tarltons. Possibly the museum (but its a stop in the tour bus thing).
is there any other big main touristy things to do??

but what else is there that will be open in early Jan?
the campsite at R&V's shuts on the 2nd Jan so we would head to auckland that day and stay in auckland until maybe the 6th.

is there good cheap accommodation anyone knows of?
we dont have kids but would like an actual bed (not bunks) and prefer a small bathroom in our room but we arent opposed to a backpacker hostel and communal facilities if its in a nice safe location.

and now does Public transport work? would we be better to get a daily pass thing each day we are travelling? or to just get a cheap as rental but then have to worry about parking costs too.

sorry for the million questions.
(I have also asked on TM msg-boards)

It will be school holidays, so much of the children tourist things (Rainbows End) might be mad!

I dont know if you are into it... but you could always take a ferry ride to one of the islands, Waiheke - Rangitoto (hike/walk), Great Barrier - Even Devonport can be nice to walk around

Then there is all the beaches - up north for white sand (mainly) or out west for Piha, Muriwai or Bethells.

http://www.maxx.co.nz/ Can hopefully give you ifnormation about best bus/train things and price

we talked last night

and we are now thinking of going and spending 2 days up in the bay of islands to do a fishing charter, and maybe 2 days in rotorua to do hot pools and luge

but will stay in rotorua for 1 maybe 2 nights to still go to rainbows end and see the sky tower.

no idea how we will get around though, as we cant pick up a rental car in gisborne beacuse is 2nd jan so the places are shut.
but we can get a ride to rotorua or tauranga from a mate