Papua New Guinea's Orchids opened Saturday's double celebration with a 58-4 win over France, followed by the Kumuls' 42-18 victory over Lebanon in Port Moresby.
Rhyse Martin scored a try and converted all seven of his team's tries at Santos National Football Stadium, finishing with 14 points in his farewell World Cup campaign.
The 22-Test veteran plans to retire after the tournament and become football manager of the PNG Chiefs, who enter the NRL in 2028.
The Kumuls led 18-0 after 30 minutes, with tries from five-eighth Gairo Voro, winger Robert Derby and second-rower Nixon Putt.
Voro, 23, spent two years with the PNG Hunters before joining the London Broncos in Super League's second division under coach Jason Demetriou. He has a Chiefs development contract and will learn from Jarome Luai.
Lebanon hit back with tries from Abbas Miski and debutant Tony Sukkar, cutting the halftime deficit to 18-12. Miski later scored again, his 15th try for the Cedars, to make it 30-18.
Finley Glare and Epel Kapinias scored early in the second half for PNG. Martin's try, nine minutes from time, and two late try assists from Edwin Ipape sealed the result.
Lebanon's Jacob Kiraz ran for 207 metres, while Tony Frances made 292 metres and Alex Twal recorded 48 tackles.
The Kumuls face Samoa in Port Moresby next Saturday. Lebanon, quarter-finalists in 2022, play Tonga at CommBank Stadium on Friday night.