Mr Grant suffered the worst injuries - to his hip and leg.
He and his partner Gemma Askew are vigilant in ensuring their two children, Cooper and Chelsea, 1, follow the family edict that they must be buckled in before driving away from home.
The area of the car where Cooper was sitting took the brunt of the impact and Mr Grant said he had immediately checked his boy.
"I thought 'thank God he is okay', that was my main worry."
Mr Grant was trapped and had to remain in the wreck until a fire crew arrived to cut him free but his friend Mr Karaitiana unclipped the little boy from his child restraint seat and sat with him to keep him calm.
At home, Ms Askew was alerted to news of the crash by Mr Grant's father who had been contacted by staff of Hiremax, a business adjacent to the crash scene, and he was able to allay her fears that her son or partner had been hurt.
She said the couple own two cars and both are fitted with child restraints not only to obey the law but primarily to protect the children from just the sort of incident that occurred on December 23.
The new manager of Wairarapa Road Safety Council, Bruce Pauling, said yesterday that the Waingawa crash was a classic example of how vital it was to keep children buckled in.
"The restraint laws are in place but safety is the first priority and we want all families to enjoy their travels, especially at this time of the year.
"Crashes are likely to happen anywhere at anytime and each time a child is travelling in a car they must be in an approved child restraint."
Mr Pauling said he was in no doubt little Cooper would have been badly hurt had he not been properly restrained and he was so pleased with the family for taking correct measures to protect their children that he gave them petrol vouchers as a sign of the safety council's appreciation.