The number of scenarios should be around 3-5, too fewer and you don't have a range, and too many more and there are too many to understand. Additional choices might be something involving an unlikely event but one that would have a large impact. As you work through various scenarios, you get an understanding of events and possible combinations. There are many ways to have group involvement in making change or developing goals or other targeted activities. The search conference approach began in the 1960s and improves on these techniques but many of the features are found in other approaches.
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This is not really a standard futures technique. That is very valuable in looking at futures issues. They are very useful to get a feeling of what people think about issues. This indicates to you if you should use an educational program of a certain type to change attitudes, market your services to how people are already ready to receive them, or if you should give up on what you were planning to do because the group you surveyed is not ready for that. If you want responses of this type, it is a very good technique.