On Groupon you can purchase a 2012 and 2013 Season Pass to Cowabunga Bay for only $59! And, since they are open select days in September 2012, you can use it right away. And, you will be set for next Summer too.
I think this place is great for younger kids. It is easy to keep your eye on them. Plus, they have a small kids playing area that is just for them.