We went to Aulani for our HM, but got married in WDW first. We were there 10 days and saw weddings daily but only saw one wedding on the actual beach (a small public beach we walked over to past signs warning us we were leaving resort property). It was definitely an unplanned wedding- the bride changed into her dress behind some bushes and about 20 people gathered around them and got married right at the water. We were the only ones around because we had gone exploring. Any of the chapels that aren't disney I think only do the weddings in the actual chapels. We didn't see any disney weddings on the beach but I assume theyd be the only ones to set that up in the Ko Olina area. Good luck!