Fantastic place for the kids. I hadn't been back since i was a child so I was completely blown away. Lots to see and do. We went on a Saturday and as greeted with quite a line up to get in. Once in however, there was never a wait for anything else...except for the pandas of course.
My only suggestion would be to go on a day that isn't too hot because the animals seemed very inactive. I heard again and again "Animals aren't moving....too hot out here.". Who knows if it's true but going back when the weather is cooler wouldn't hurt!!