Mr Trim said there were major benefits in staging it at the new sites.
"Some infrastructure is already in place at these venues, such as power and toilets," he said.
"We always had to start with a bare patch of ground at Anderson Park, and work for three days to transform it into a viable event space."
Before he took the reins of the event it had been attracting 4000-5000 people but he said he wanted to create a more professional event and take it up "another notch".
This year's big outing will see more than four hours of stage entertainment featuring two high profile acts, as well as the Mahons Fairground, obstacle courses designed by army territorials, food courts and a grand fireworks finale created by the Kaisen Trust and choreographed to music.
"We are grateful to Napier and Hastings councils who will both contribute financial support to Christmas at the Park, regardless of which city it is being held in," Mr Trim said.
"This is a fantastic example of how unity can be achieved - as collective cities we will have a major event."
An added advantage of staging it at the showgrounds this year was that it would occur at the same time as the annual Fiesta of Lights at Waikoko Gardens.
Both cities would continue to stage their own individual Carols in the Parks events - Hastings at Cornwall Park and Napier's at the Botanical Gardens.
"This is great for the region," Malcolm Cox of major sponsors Cox Partners said, adding he was enthusiastic about continuing to support the event.
He paid tribute to the work of Mr Trim and the Kaisen Trust.
"This is a not-for-profit event which relies on sponsors, voluntary contributions and trust funding."
Mr Trim said he wanted to maintain it as a free event with a family feel.
The main spectator area would be the grass showground arena, with the 3500-seater grandstand an additional bonus. The stage area would be set up in the corner at the south end.
A&P Society chief executive Brent Linn said he was pleased to see the event come to the showgrounds.
"This potentially will be the biggest one-day event we have ever held.