I'm thinking of doing this for the plastic cauldron I use to keep my candy in. Currently I have it on top of a fire pit made with the great stuff foam and orange christmas lights. The kids then have to reach in to the "cooking" pot to get their candy. It looks pretty good but the kids are definitely not hesitant as I had hoped they would be. I would have to have some type of mesh screen above the dry ice and water for the candy to sit on. A couple of people are always sitting around the fire so they could easily run the bubble mixture over the top whenever they see a kid approaching. My question is how much dry ice do you think I would need to last 3-4 hours. I've used a lot of fog machines but never dry ice. The cost and convenience has always kept me away.