If you'd love to add a little more culture to your trip, put KDs Elvis Presley Museum on your list. Check if guided tours are available or just wander around in your own time.
You'll have no end of sightseeing choices in Hawera. KD's Elvis Presley Museum is an ideal place to start here, but there are loads of other worthy places to explore. Hawera Water Tower, Hawera Golf Course, and Tawhiti Museum are near the museum and and will cap off your day nicely.