Christchurch (Cheech) is fantastic, the Park Royal (I think it's now the Crowne Plaza) is probably the downtown flagship lodging. The Kroyden or the Windsor are modest B&B's that are good, but last time I was there, I don't believe any of their rooms had private baths.
City bus to and from the airport is easy, goes right downtown, and most anywhere else you might want to travel, lots of other good public transport (SuperShuttle, etc.) if the hotels don't have a van.
Botanical Gardens, Lyttleton harbor, Akaroa, Banks Peninsula, Antarctic museum, lots to do right around Cheech; night life, all kinds, The Carlton, and Charlie's (of course I've never been, but I hear tell....), Dux Deluxe has great beer (most of NZ does) and good dinners, but it's veggie or seafood. It's been a few years, so my info may be outdated. Have fun, cheers, mate! (I'm jealous, have a pint of Lion Brown for me!)