Ōpōtiki to Te Araroa
This is generally flat with one steepish hill (218 metres) at about 30 km at Hawai Bay. Te Kaha has a store, takeaways, café and campground and is just across the road from a lovely bay and headland. There is a fairly flash beach resort that does an elaborate breakfast if you want to splash out. It also displays some early photos of whaling in the area.
If you want something a bit closer to Ōpōtiki, try Hawai a pretty bay with access to the river but not suitable for sea swimming (30 km). Omaio (57 km) has a shingle surf beach and a reserve (Hoana Waititi) with basic camping facilities (toilets/water) and a store and café close by.
This is a relatively easy gradient alongside the coast for about 50 km and then the road turns inland just past Whangaparāoa (Cape Runaway) and you encounter a few hills before Hicks Bay (store, takeaways, hostel). Hicks Bay is lovely, but the main beach is some distance off the main highway and you may wish to continue over the hill for about 9 km to Te Araroa (campground, store, takeaways, gas station, pie-cart café). There is a nice café at the Visitors Centre just this side of Te Araroa.
If 90 km is a bit long for a day's cycle you can stop at Maraehako (20 km from Te Kaha, campground, backpackers). Waihau (campground, store and café 30 km from Te Kaha). Oruaiti Bay (40 km from Te Kaha, campground).
At Te Araroa you have the option to cycle to the most easterly part of the world (apparently) and visit the lighthouse. Arrive at dawn and be the first in the world to see the sun rise. A 40 km round trip.