Hi L.,
We just had a Mad Science party for my 7 year old son. We used the Mad Science of Dallas. It was quite a hit with about 18 children who were all 6 and 7 year olds. I rented the Armadillo Room at the TMC in Plano which worked out perfectly. They had sink and electrical outlet which was a necessity for the scientists. A few things, we had a large group and I anticipated that they would not all arrive right on time. So I put a science table out with about 4 or so activities. For example I had lab aprons to color with fabric markers, molecules building(toothpicks, tootsie rolls and gumdrops worked well). and magnet discovery. It occupied the first 15 minutes until all arrived. The scientist was great but we had an active bunch and an assistant would have been helpful. I did the platinum plan with two extras. The balls and the cotton candy. We had about 15 extra minutes after cake so the table came in handy again I am not sure that I would do the balls again, between cake and cotton candy there were 18 balls flying all over the room because of the sugar high. His part took up about 60 minutes, I thought it would be more like 90 minutes.
I would recommend Mad Science in general but with some caveats. It was more work than expected with such a large group but the kids loved it. I would be more than happy to offer more details off line. I did some creative things for cake and drinks that the children liked and passed some times as well. Email me at ____@____.com you have any other questions.
T.