Having a little business myself i found it really interesting seeing where it all started from and how it grew to what it is today!
It mainly centers around the historical side of things but is definitely worth a visit especially if you can go on a week day when they often do 2for1 tickets.
The one thing I felt was missing was more interacttive activities for kids. There's a lot of little historical presentations, people dressed in costume from the era and a few computer/technology games at the end but I did think there would be more involvment where you got to see and have a go at chocolate being made.
Overall we had a great day out though and free chocolate bars were a bonus, the Cadbury's shop is great and I stocked up on hot chocolate. You can get things cheaper than the shops too like the giant 1KG bars that come in the boxes so good for gifts.