Concur that Waikiki is the place for you. 30 foot waves will hit north shore this Wednesday and Thursday. Don't even think about going out. If you drive up there, expect big crowds and having to park on the side of the road and walking a long ways. Or, go very, very early in the morning to find a good parking place.
The west side of the island will be big also, but the locals are not friendly to tourist in the water. Don't go there either.
There is a nice beach that a lot of people are learning to surf at across from Sea Life Park and that should be good.