Be reasonable about duration. People who volunteer their time to attend a Citizens Police Academy are inherently curious and willing to give their time to have that curiosity satisfied—but everyone has their limit. Six sessions of three hours or nine sessions of two hours—or somewhere in between—is probably the sweet spot.
Most of the academies I've attended have been eight two-hour sessions. One had an elective session that lasted six additional hours on a Saturday during which attendees were given the opportunity to participate in live fire firearms training. This is next-level stuff, and not necessarily for the agency holding its first-ever CPA.
Be thoughtful about curriculum. If you have an academy of roughly 18-20 hours as suggested above, you need to be really circumspect about the curriculum. There's no way you can cover all the ground you'd want to, so be selective about the subjects to be covered, and much of that decision-making process will be determined by what's seen by your local press, politicians, and public to be most meaningful to them. Here's a short list of ideas:
Department History: Begin with at least some time spent on the history of the department, including its inception, significant milestones, as well as full disclosure of any perceived blemishes on its past. Appearing to sweep under the rug an incident—however many years have passed—will undermine the integrity of everything that follows. Plainly own your past, and clearly articulate your future.
Use of Force: Included in this block should be agency policy, training standards, applicable case law, a case study of an appropriate use-of-force incident (preferably on video). A great option for additional training would be held at the academy, with time in the mat room as well as the force options simulator.
Community Policing: At its core, a CPA is community policing 101. Those who are in your classroom for the CPA are willing participants in that process. Give them the tools and resources to expand your community policing efforts with information about National Night Out, Shop-with-a-Cop, or anything else you do to connect with the people of your city or town.
Equipment Display: A lot of people who have interest in policing also have significant interest in the gear officers use in their daily duties. One CPA I attended had all the students assemble at an outdoor location where a mobile command post, an armored vehicle, an array of weapons, and ballistics protection were on display. The instructors that day were all SWAT or command staff, and each was there merely to answer citizen questions—there were no prepared remarks.
Career Day: Have representatives from all your specialized units come in for a brief firsthand explanation of their assignments followed by a quick Q&A. Bring in a K-9 and handler, a crime scene analyst, a 911 call taker, a SWAT operator, a school resource officer, as well as someone from bike patrol, marine patrol, and motor patrol. This should be a cadre of volunteers who have been well vetted.
Choose your instructors wisely. In an ideal world, the officers who teach most of your Citizens Police Academy will be individuals who have a role with academy, in-service, or FTO training. There should also be a handful of command staff who are tasked on a daily basis with implementing policy. As was indicated above, you will also probably need to have individuals who are not on the training team present at least some content. Give them any necessary training to present their content in a way that reflects well on your agency.