Southern Hawkes Bays is blessed with a great network of quiet, back-country roads. There are many options for heading south, most of which will lead you through quiet, rural settlements, generally ending the day at a stunning east-coast beach. This route suggestion is just that - a suggestion. There is plenty of scope to do your own thing. But whichever way you go, make sure that you leave Napier with enough supplies to last for at least 3 days. The next supermarket isn't until Masterton and you will encounter only a few stores offering basic supplies.
Napier itself has a great network of cycle trails. It's a good idea to have a map at the ready just to keep you heading in the right direction. The Hawkes Bay Regional Council has a map online although you should also be able to pick up a copy from the information centre.
To head out of Napier follow the coastal cycleway as far as Clive, then take a left onto Mill Rd, continuing onto the lightly trafficked Waimarama Rd. You will pass the wine growing region of Te Mata, continuing on a generally quiet, rolling road for the next 50 or so kilometres as far as Elsthorpe. Here you have the choice to follow the smoother, fully sealed, inland road through Patangata (pub) or instead take the more scenic, but slightly longer and more undulating route through Kairakau Beach and Omakere, which is unsealed in parts.
At Omakere you may be lucky with the tides. At low tide you can ride along the hard sand directly to Blackhead Beach.
Blackhead Beach offers beach-side camping with safe swimming at the edge of a marine reserve. A beautiful spot but there is no store and you will also need your own cooker as the campground here does not offer cooking facilities.
You may wish to break up this trip with a stopover en route. There are plenty of options available, with camping at Clive, Haumoana Domain, Te Awanga and Clifton. Informal camping is also available further down the coast at Ocean Beach, but informal in this case means solely at the discretion of the Ocean Beach surf club. The camping area is on private land adjoining the club house and the owner has given permission for the club to use it. Ask and it shouldn't be a problem.