Auckland Mayor Len Brown will speak at the event to offer support for the project, which depends on finance to be raised by Orewa-based Hopper Developments from an institutional investor.
A joint venture of Hopper and a walking and cycling trust wants to charge tolls, starting at $2 a crossing for holders of public transport Hop cards and $5 for casual users such as tourists, for 20 years before handing the pathway over to public ownership.
But that was vehemently opposed by transport committee member Cathy Casey, who said people should be able to cross the bridge free of charge.
North Shore councillor George Wood raised concerns on technical grounds, saying his constituents would not tolerate the addition of any structure which may weaken the structural integrity of the clip-on.
But Transport Agency regional adviser Chris Gasson confirmed to the committee that a preferred engineering option negotiated between the pathway group and his organisation "doesn't ultimately compromise the bridge".
The option would allow for a pathway of up to 4m wide, narrowing to 3.2m on the seven-span bridge's three northern spans, but with crowd management to limit loads on critical areas.
Engineers calculate the number of people allowed on the structure if traffic loads grow by a predicted 10 per cent by 2031 will need to be capped at 300 to 400.
Councillor Dick Quax questioned the point of the project if numbers had to be restricted, but pathway representative Bevan Woodward said five times the maximum would be able to cross the bridge every hour.
His group believes daily numbers from 1052 people in winter to 2520 in summer will be enough to cover the cost.