There's a lot of things going on in the Valley. From snacks & sweet shops to all the water activities. Avoid weekend if you can, as the area can be filled with too many teenagers and kids. The music was the same everyday, and it was loud.
The wave was ok, but the highlight for us was the temple of courage. It felt like a free-fall roller coaster ride down the water. A little scary, but makes you want to keep on doing it.
Entry is free for all hotel guests. Towel was free with a refundable deposit when we stayed at the Palace. Not sure about other hotels though.