Is the advice you are looking for more on the delivery side of things, content side of things, or both?
Would this be your first time teaching something to a group of people or do you do this everyday?
I ask, because I don't want to give advice you might already know. I have had multiple instances of teaching groups of adults and kids, but I am not sure of your capacity or experience with teaching something. I am willing to offer plenty or tips and information about content delivery if you are rusty on that.