There are powerpoints on ultiflop for all the classes. You Tube has things that can be used in lessons as well, these appeal to different learning styles.
Prepare a time line in ten year intervals with boxes underneath and give them a jumbled set of numbered sentences relating to RAF history and they put the corresponding number in the box. You can turn this into a powerpoint slide with all the points going to right spot.
I’ve did this with history of flight when it first came into the syllabus. I don’t teach this anymore, but it seemed to work.
With respect to keeping them focussed, think of school. In a class of mixed ability kids, like we have with cadets, keeping them interested / focussed can be a struggle for even the most experienced teacher. I’m sure you’ve been in classes at school where the teacher is a good teacher, but certain kids can’t be bothered so play up and teaching is lost. If they get too rowdy send them out for a chat with a member of staff.
The thing to do is research the subject and think of things that would keep your interest, and in researching, bring extra knowledge that stimulates debate and questions. I’ve taken 2 or 3 sessions to cover something that some cover in 1, because I’m relaxed with the situation of questioning and debate if the cadets are taking more away from it.