Valuable comments and reflections from Steve Russ on an earlier draft:

• High risk of wasted effort unless sure of being well-informed on situation and expectation of visitors - and how well-informed in advance they can be ... (perhaps no guarantee of that at all).
• It seems to require attendance at specific time (for background intro) before the real game session. All part of one session I understand, but if some are late ... very difficult. Have to reduce dependency on 'intro'.
• Have people travelled far, or are most local? Do visitors sign up in advance for workshops? Can you expect takers morning / afternoon / Thur / Fri? Do visitors get to see the descriptions in advance, on web, on a leaflet on the day etc?
• All the lessons of experience suggest when so many unknowns (age, continuation after event, existence of prize etc) that 'simple is best'. But adventure theme - and your description sounds good.
• It may be that an event like SciFest only affords superficial engagement. If so, then the goal is to do enough to get them some involved later at home (as may be your plan). Some online help may be appropriate.