Attend the October granddad of all ironman races worldwide, right in Kailua-Kona. Book your accommodation well in advance
There are many other things to do such as ocean kayaking and horseback riding in ranch country. If you are looking for something in particular, please email me. Don't forget to try just walking around viewing island life and relaxing.
Try some of the island's huli huli chicken roasted outside under the Hawaiian sun on homemade multi-spitted barbeques