Aloha from a fellow Hawaiian Bride. I am getting married on Waialae Beach but doing my TTD on Waimanalo Beach. My WC recommended that we do it there because the beach is beautiful and she said if we do it early enough that there wouldn't be a lot of people.
The beach is really long, so it works well for a beach wedding. Also I think that if it is her first choice for beaches on Oahu, you do not have anything to worry about.
Well I hope that helps. Let me know if you have any other questions and I will let you know how the beach looks when I get back.
Happy Planning.