We go every year. Be prepared for some very friendly animals sticking their heads into your window. I typically recommend taking a truck and throwing everyone in the bed. I still find feed from a couple of years ago when one of them scared my wife and she threw the bucket all over my backseat.
I can tell you CJ the camel can and will reach his head from the driver side window to the floor board on the passenger side of a Toyota 4Runner in order to get the food bucket. This may or may not terrorize your young children when he proceeds to do it.
It is great! And be careful if taking small kids in the "baby animal room". Some of them are a little rough and bite. If you are worried about your car getting messed up they can take you in one of their vehicles.
I drove through one outside of Waco. Animals would take turns standing in front of the car so you could not drive away. I inched my car forward and was touching a mule and he did not move until we dumped all of our feed out the window.
Went a couple of years ago with my wife and father. We had a great time. When we were leaving, some guy was about to enter the park in his brand new Mercedes convertible (top down) with his girlfriend or wife. I was like, "Oh, no, man. Don't do it."