Well, in case you have mentors…
At the start: why not invite mentors and other interested/interesting people to come and have an open discussion with jammers before the Secret Jam Theme is released? Invite experienced designers to present the phases of design process and the weekend time line. Keep it casual and open to questions, but make it brief—there will be reminders along the way.
During the Jam: method input before every phase (2–3 minutes). Let mentors with specialist knowledge quickly explain the next steps. See also tools ‘Rotating Mentors’ and ‘Feedback in between’ in Tools and Guides for Mentors.
At the end: perhaps your mentors can give prizes to some teams, or assist in choosing your overall winner, if you have one.