Legacy Funerals funeral director and operations manager Don Hoult described the tributes as "some of the best I've ever heard".
"I think with what they said and the love they showed, they were just amazing," he said.
The children spoke of their parents' selflessness and passion for helping others and of their comfort in knowing their parents had died together, doing what they loved.
The Johnstons and Ms Dickson were in Kenya to help build a new classroom block at the Ark Quest Education Centre in the western Kenya village of Mahanga.
They were part of a group of seven adults and 12 students from Bethlehem College.
The couple were considered to be founding members of the Bethlehem College campus and heavily involved in the school, where two of their children still attend.
At their funeral crowds overflowed from the 1300-seat events centre into the school's performing arts centre.
Dr Johnston was an anaesthetist at Moving ceremony for Johnstons
the Bay of Plenty District Health Board. The day he died was the 26th anniversary of his appointment to the role.
Following news of the Johnstons' death, staff at Tauranga and Whakatane hospitals said the couple were "woven into the fabric of the Bay of Plenty" and would be sorely missed.
The Johnstons were members of Greerton Bible Church, which they had attended for more than 20 years, and were a well-loved, key part of the church family.
Pastor John Elen said in the days following the deaths that many of the congregation were numb with shock.
As the caskets were carried from the events centre, members of the school team performed a haka for the Johnstons, who had been big supporters of the team. Members of the Otumoetai Eels Rugby League Club also performed a "surprise" haka in front of the two hearses, Mr Hoult said.
The Johnstons' sons Mike, Phil and Chris are all players. "It was a very moving ceremony," he said.
Bethlehem College principal Eoin Crosbie flew to Auckland following Saturday's funeral to meet the third contingent of the group returning from Kenya. It is understood the latest group included the most seriously injured in the accident.