Please no gifts (seriously). We are not young newlyweds and have accumulated more stuff than we need. And given the time, cost, and effort of getting to Hawaii, your presence is the only gift we desire. We really mean this, if you give us a gift, we will feed you to the sharks.
That is entirely up to you. Note that we will have some optional activities leading up to the wedding (see the tentative schedule). And it is Hawaii. Feel free to make it an extended vacation if you can. Go to another island (we love Kauai). Linger on the big island. Soak up some sun.