It's mainly staffed by volunteers, who are paid where possible. Mrs Ranginui can staff it at weekends, when she is not working for Te Oranganui Iwi Health Authority.
She's the Whanau Ora practitioner for people from Parikino to Jerusalem.
She said the former school building that houses the gallery has a long history.
It was moved to Matahiwi from Parinui, further up river, in the 1940s. It closed as Matahiwi School in the early 1980s, and for the rest of that decade was one of the Whanganui River's first kohanga reo.
The kohanga moved to Ranana around 1990, because there were not enough children at Matahiwi. The site belongs to Matahiwi Marae, and another building on it was used as a correspondence unit for teenagers. That closed in 1993, and its building is now a health clinic.
Through the 1990s the former school building sometimes housed Mrs Ranginui's fitness classes, and was sometimes empty. It needed a lot of upgrading when the trust decided to turn it into first a craft shop and then a cafe in 2009.
A grant from the Te Atihau Trust paid for some renovations, and locals pitched in to help.
The boat that featured in Vincent Ward's River Queen film is sitting outside, courtesy of Koriniti business The Flying Fox, with a roof over it to preserve it.
The gallery sells weaving, carving, paintings, pottery and cards made by local people.
Some of the paintings are by Colin Gibbs, a former artist-in-residence at Ranana's school. There are also free range eggs and fruit for sale, in season, and staff can answer questions about Matahiwi and the river.
"People mostly just ask about the school and marae," Shantel Ranginui said.
The cafe's 20 seats have occasionally all been full, and Mrs Ranginui expects that to happen more often.
"It's picking up this year, and we expected that."
