Forgot to mention, worth a short trip from Raglan to check out Aotea Harbour and the sand dunes. Also historically siginificant for waka/canoe landing (as is Kawhia).
A great weekend option to take HWY22 to Raglan from Auckland, and then do this ride the following day. If you are based in Raglan you can start from there and take in Waitomo Caves (world famous blackwater rafting) along the way. The route gives you a few options, but the less travelled road is not quite as good as the main roads. All fine, but camber is slightly better as is road surface if direct route from Raglan to Kawhia is taken. Enjoy the day