After graduating, Havini was employed as an adult education officer and helped establish literacy courses and facilitate correspondence studies for Bougainville residents.
He successfully lobbied Papua New Guinean education minister Ebia Olewale to establish a school for members of the Hahalis Welfare Society.
[3] As an executive officer of the Bougainville provincial government, he was involved in development initiatives, such as the establishment of a fishing industry in the outlying Green, Carteret, Takuu, Nukumanu and Nuguria islands.
[8] In 1975, following the unilateral declaration of independence of the Republic of the North Solomons, Havini was named as a member of the executive of the interim government, serving as an assistant to chief secretary Alexis Sarei.
[10] In January 1976, while protesting in the village of Hutjena, he was shot in the back by rubber bullets fired by the Royal Papua New Guinea Constabulary, an injury which took nearly a year to recover from and left him with a large scar.
[1] Havini attended the 1991 Commonwealth Heads of Government Meeting in Zimbabwe to lobby for an end to Papua New Guinea's blockade of Bougainville.
[1] In July 1971, Havini married Marilyn Miller, an Australian women he had met while attending a Christian students' conference in Melbourne.