How do I tell a customer that I don't want to do it?
I don't have any reason other then the fact that I don't want to mess with it, seems like to much of a hassle for 30 servings of cake.
I don't mind doing the cake just not the dry ice....thanks again Duff

let the customer take care of that

You make and decorate they cake make a hole for a container and place it in the cake and then they can go buy the dry ice and put it in water in the cup. They have the hassel and danger and everyone is happy.

I agree. If you do not want to do the dry ice part, just build the cake with a spot for the dry ice. There are instructions on how to make fog at this dry ice website. Basically, I would tell the people that they can buy the dry ice and keep adding it for the effect.