We were just there this past week. My son and I arrived at the beach about 10 minutes before the water parade and there were still chairs available. We shared a chair (he is 5, so he sat on my lap). We sat on the beach a bit away from the pool area - it was less crowded on that end. You can also sit right on the beach.
If you haven't made plans for dinner yet, Kona and the QS place are very good. Poly also has a great lounge. Although we were able to grab a beach chair right before the show, the Poly is so much fun just to walk around, so you may want to go early and enjoy the resort a little before the shows!