I was there yesterday. I am staying onsite so I was able to arrive at 8:30 and enter immediately. I rented a cabana and I checked in at the first concierge booth. They then sent me to another booth where I waited again. I asked about express pass and that is $35 a person. I did not get it and we did not need it. There was no preferred seating or cabanas available - they were sold out. If you want either you should call today.
If you are not getting preferred seating I would not get a chair in the pool area. It is wide open. We were in a kiddie pool area and it was not a crazy busy area, and families loved the chairs in that area.
We started in the back of the park with the Ko'okiri Body plunge. Wow! There are a lot of steps to climb! The only attraction that had more than a 45 minute wait (and that was after 1:00) was the Ohno, which was almost two hours. We planned lunch and pool time during that time.
One word of warning. We did the fast "lazy" river in the morning and it was fun. We did it again in the afternoon and it was crazy (really bad). There were about 75-100 people in the water looking/fighting for tubes. As people came by, trying to exit, people were there tying to grab tubes, fighting each other for a tube. Some people got stuck and got swept into the water. As they swam by the lifeguards would yell at them to get out, that they couldn't be in there without a tube. No one did anything or helped them. I do not think they were in trouble there was just no way for them to exit if they wanted to.