Personally I think that's a long drive for a nice view, but your missing so much by getting all the way to Arthur's pass and not going on any hikes... But then again you don't have that luxury of that kind of time on a cruise. (We spent 8mths towing an 8m travel trailer around the South Island)
For us Lyttleton is nice but won't fill a morning even if the market is on... There are a few nice walks up in the hills especially around the gondola but it's a mission to get to without a car.
I personally would get to Christchurch and do the tram around town find a nice bar or a bite at riverside, Christchurch city area is mostly new and flat and easy and has a pretty river running through it. There's more than enough to fill a day in Chch.