My DD did it in 2005, she was almost 5 and loved it. I think its about an hour, they had storytime with Alice and the MadHatter, the tea party and had a special item for their mommy. I left a disposable camera and the CM's took a couple of pics, they all have one done with Alice and the MadHatter that was included in the price.
Parents are not allowed, I just went and had tea in the cafe. It is a cute party and I recommend it if your comfortable with leaving your kids.