Wedding will be in Kilauea. We recommend staying in Princeville as there are many hotel, AirBnB and condo options, although Kapaa is also close enough to the venue and with hotels as well. Please check distance from hotel to venue to ensure drive time is not too far. Poipu is a popular place to stay, but it is a very long drive.
We highly recommend having a rental car as services like Uber are not always available. There is some uber, if needed to get to your hotel or rental car, but some areas of the island are remote so having your own vehicle is best.