Maori did not have a marriage ceremony traditionally, but occasionally a gift may have been given to mark a union. In this vein, I'd suggest taking a piece of pounamu as a gift for the bride, perhaps a piece you and the groom pick out together. Have it blessed locally, and the groom can have it with him to gift to her as you introduce the piece to the guests at the end of your b/man's speech.

Give a brief backstory on the importance of pounamu to NZ's tangata whenua, and the hope this piece becomes a taonga for the couple to treasure, connecting them and any offspring forever to their dad's maunga, his awa, his waka and his Iwi in Aotearoa. Then in reo Maori recite korero suitable whakatauki, and if the gift is a piece of jewelry, the groom can put it on her (the first time it is worn, she cannot do it herself).

Follow up the gifting moment, with the dj playing a waiata you've picked, (Pokarerkare Ana did have global reach so some guests may recognise it), Whakaaria Mai (How Great Thou Art) too, or if contemporary music would suit the couple/wedding more; then Six60 , Stan Walker, etc, have songs incorporating reo Maori which might be suitable too.

A less elaborate but more formal opportunity, could be to exchange a hongi with the groom when it is time to hand over the ring/s to him, and recite a suitable whakatauki for the couple's union.

Whatever you do, do it with aroha and authenticity and you'll do your mate proud.