Every session do two things:
1). Teach a lesson. Something simple like the first 3 moves of a standard opening. Keep if brief. Next time review the old lesson and do a new one.
2). Play a schedule of games, preferable everyone plays at the same time on multiple boards, and keep records and standings. Competition brings out the best in people. After the games review them as a group and discuss where the game turned or was decided.
Actually a third thing: Keep it fun.
What town and state are you in?
pretty small town in Indiana