Ms Mount said her clients' reaction to the law change has been positive - which surprised her, as some parents were less than impressed when the new rule was announced.
Previously, she said, some families had said they "couldn't be bothered" seating their older children in booster seats, or thought raising the age limit was "overkill."
"There was definitely a bit of negativity leading up [the change]. But it's been very well received. People have just accepted it."
"We sometimes get people coming in and saying things like, 'how are we going to fit three car seats in the car?', or 'we can't afford this' or 'is this really necessary?"' said colleague Cherie Wall.
"But we just explain to them that adult safety belts are not safe for children, and what can happen in a crash.
"Then they go, 'oh, okay. That makes sense.' It's great to see those 'a-ha' moments."
Ms Wall said Plunket offers a layby service for families struggling with money, and can help clients prepare letters to WINZ requesting grants for a car seat. It also sells child safety harnesses, which fit over each shoulder and are attached to the vehicle's lap belt, and can be safely stowed in the glove box.
Another common concern for parents is wrestling their over-5s back into a booster seat - but the technicians say children have been enthused by the the prospect.
"We do sell some cool seats," said Ms Wall.
"The kids will say, 'Oh, my friend's got that one.' Or, 'can I have that seat in another colour?"'
Ms Wall and Ms Mount say the rental service had been struggling, as parents had been unaware of its hours or location - but business had improved following coverage from Wairarapa Midweek on the service and the child restraint laws. In fact, it has recently increased its weekly opening hours. "It's just skyrocketed," said Ms Mount.
The rental service also hires out capsules for newborn babies and child's car seats for older babies and toddlers.
The car seat rental service runs out of the Wairarapa Community Centre, and opening hours are 10am to 2pm on Tuesday and Thursday, and 5pm to 7pm Wednesday.
For more info, call 06 378 6101.