Do you mean Hershey Chocolate World?

I have taken my 9-year-old daughter and some of her friends to the design-your-own chocolate bar thing, and they had a ball. It wasn't cheap, though ($15 per person). There is also a chocolate-tasting tour, which we didn't do, and we didn't do the trolley tour either, though it comes highly recommended by a friend of ours.

The free "chocolate factory tour" that they offer is akin to the Carousel of Progress at Disneyworld -- it's an animatronic ride that has models and videos of different stages in the chocolate-making process. The kids had fun, but it's not really a proper factory tour.