Firstly if you dont charge and I assume that you don't as your insurnce wouldn't cover you for that you should ask yourself why they want ago . It is nice to offer anyone a try but if they just want a go bacause you offer it then isn't that a waste of your time .
I don't understand something else, if it is a go for "First timers" you really mean a taster session to see if they can stand, walk and jump and then try unaided.
Without your check list it is hard to see what you have missed off but for what you have put you have missed one very important thing, that fittness of the person.