Also grew up in Nelson (lovely place!!) - To Golden Bay from Nelson itself is about 1.5-2hrs... Kaiteriteri is a great place to go and visit, but this time of the year I believe the population goes from around 2,000 to 10,000 people all jammed into baches (/mansions) and the camping ground! Its beautiful, and would be perfect if you wanted a beach and the associated activities. IF you want shopping and food - probably not the place.
I second the suggestion to base yourself in Tahunanui... Its lovely there and very central... Also has the beach (not as nice as Kaiteriteri - but still way nicer than most of the beaches in NZ).. The camping ground there is pretty good but there are also loads of motels etc.
Golden Bay is just beautiful.. Go and check out Pupu springs (clearest water in NZ or something like that)... Go over to Mapua for lunch (either fancy fish and chips or one of the restaurants on the wharf)... Have a look at Eyebright and all their xmas decorations (thats just out of Richmond).. Eat at many of the lovely places in Nelson (I love the Morrison St Cafe, the Boatshed in Tahuna is very expensive but very delicious!)..
All this is making me so homesick! Enjoy your holiday