I've never seen Seiryu Stones there. There is usually a shrimp breeder too, but he wasn't there at the last one. Last minute cancelation of some sort. I'm assuming since he missed the last one that he should be at this one.
These are great opportunities to bring the family out to. Just a word of advice, it does get REALLY crowded at first and the aisles are narrow so it makes it a little difficult to navigate through. But all in all, it's well worth checking out