I can think of quite a few ways to fill in a day in and around Napier (and a day is all they'll have). For example (and I could come up with more with a few minutes thought), art deco walking tour. Wine and/or food tour with any number of outfits. Or self guided wine tour (but need a sober driver). Walk to Cape Kidnappers. Or play a very expensive round of golf at the golf course near there. Drive to Waimarama Beach.