As I said, it is your call and much will depend on what you have available and can set up. Given that we are in the church hall, that will rule out some of the messier things which you have done, such as with the colour water splashing into the wine glasses.
I would be interested to see the rim lit effect if that is possible.
I think that some sort of introductory talk will be useful as it will give people a better idea of what they need to do for themselves. Otherwise, it will just be people milling around trying to get shots and not having that interesting an evening. The talk does not have to be anything fancy and as you have been doing this, you will know all the information. If you do not have time to do a PowerPoint, just jot the key details down on a piece of paper as an aide memoire.
One thing you could think about, although I do not know how practical it would be, would be to put each set together as part of the talk. That way, people will get an idea of what is involved.
What it will need is some kind of structure, otherwise it is going to be like herding cats.
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