The Budget package came after a post-election pledge from Prime Minister John Key that reducing child poverty would be a top priority.
Finance Minister Bill English said the package balanced supporting low income families while ensuring there was the incentive for parents to move from welfare to work.
While thousands of the poorest Northland families would get up to $25 extra a week they would also have to go back to work sooner.
While the package was a "significant start", Mr O'Brien worried it had taken 20 years of campaigning to get to that point.
"The really critical issues will be to ensure this is a starting point not an end point," he said.
Though the extra $25 a week would help families, it did not necessarily mean it would be enough to lift them above the poverty line, Mr O'Brien said.
The requirement for parents to go back to work earlier was also problematic, he said.
"In Northland, it seems to be that the jobs issue, and what that means for single parents, is very significant."
Mr O'Brien questioned whether there were enough jobs in Northland, granted a recent spike in unemployment at 9.9 per cent.
Also, the jobs available may not be suited to people with families, particularly in rural areas, he said.
He echoed the concerns of Whangarei Child Poverty Action Group member Ngaire Rae that the move "denigrates" the choice some parents make to stay home and look after their kids.
"To see that as the only way forward to improving wellbeing for children is problematic," Mr O'Brien said.
"We have some real concerns about what that means for children."
Speaking at the lunch were three leaders from around the region who participated in the Northern Advocate's Dear John campaign last year.
The campaign had leaders at the forefront of child poverty write a letter to John Key with fresh ideas for how child poverty could be addressed.
Speakers were Manaia Primary Health Organisation chief executive Chris Farrelly, Moerewa School deputy principal Kim Peita and Habitat for Humanity Northland executive officer Conrad LaPointe.
Budget package
The Government's child hardship package, worth $790 million over four years, included:
* Benefit rates for families with children rose by $25 a week, the first time it had risen higher than inflation since 1972.
* Low income working families would also get up to $24.50 extra a week.
* Parents on benefits now had to be available for part-time work once their youngest child turned 3, rather than 5.
* Subsidy rate for low-income families increased from $4 an hour to $5 for up to 50 hours of childcare a week per child.
