It is a pre-planned route rather than a do/not do type place.
Bear in mind the initial Inca bit can be a bit scary, although a 13 m.o. is possibly a bit young to be scared. And there is a lot of free chocolate, so with older children we had to squirrel it away fast!
I used to live near Bournville and every so often we'd walk down the canal path and go to Cadbury World - happy days!
If i remember correctly you have plenty of time to do the tour, go on the ride, mooch round the shop and spend every penny you have on chocolate. I'd recommend if you have time though having a wander round Bourneville itself. It's a lovely village with gorgeous buildings and a village green. There used to be a nice tea room/cafe just off the green - hope it's still there. Have a scone if you've got room after all the chocolate.
Take a decent sized handbag, we were given two full size bars each (crunchie and something else I think) at the entrance, including the kids, and more on the way round. You could get very sick if you hide it all in your mouth .
We had fun. You doing a weekend in Brum? A much maligned city, but I have a soft spot for it.