The adjoining Jean Batten Square has also been extended and transformed into a new community space featuring a playground and a raised crossing.
The project budget was $12.8m from the Rotorua Lakes Council and up to $4m from the Lakes District Health Board.
External funders have granted more than $1m towards special features and equipment for the library and park.
The final cost of the project will be reported to councillors at next week's Operations and Monitoring Committee meeting.
The open day will feature storytelling sessions, face-painting, creative workshops, scavenger hunts, and even a sprinkling of magic in "Fairy Corner".
There will also be plenty for adults to check out.
Dr Johan Morreau will give a live presentation of his highly acclaimed TED talk "The first 1000 days of life" at 10.30am and again at 11.45am, and 2014 New Zealander of the Year Dr Lance O'Sullivan will speak at 11.15am.
Singer-songwriter Maisey Rika will perform as well as a host of local talent, including Ruaeo Te Moni and Te Waikura Witoko of Matariki Star Search fame, Murray Clark, AMJAZZ and Lakes Performing Arts Company.
The opening will also mark the start of the Rotorua Library opening seven days a week.
The temporary library on Pukuatua St will be closed temporarily from this Saturday until the open day to allow for the move to the new building.
The mobile library service, online services and call centre will operate as usual. Due dates have been extended to February 3 for any items that would have been due during the closure, except for new release items.
The centre was due to open on November 25, but was delayed by difficulties in finding sub-contractors. There was no additional cost to the council or the DHB as a result of the delay.
The DHB will become a long-term paying tenant in the 6000sq m building, with the library taking up about 4000sq m. Some staff facilities will be shared.
The opening day will start at 10am and go until 4pm.
All City Ride bus routes, excluding Route 15, will be free on the day.
Health services at Te Aka Mauri
• Infant, Child and Adolescent Mental Health Services (iCAMHS).
• Child development team (assessment and therapy service for children with developmental issues).
• Public health nursing and screening service.
• Some paediatric outpatient clinics – those needing more complex tests will still happen at Rotorua Hospital. The plan is to have clinics on one evening a week to help parents who can't attend daytime clinic appointments with their children.
• Community oral health management
• Gateway staff (health and education assessments for all children entering care).
• Maternity advice
• Rotorua Children's Team
• Space for staff from government agencies and other services will be available on site.
