It really come down to class handling and how you set up each learning segment. The easiest way to address safety concerns is to ask the following question. Is the task terrain, traffic, and tactically appropriate? While this may seem simplistic, most other concerns can be traced back to these four T's.
Fun on the other hand is more complex because leading others to enjoying something is a combination of our actions and their reactions. Showing up enthusiastic, energetic, and excited for the opportunity to help others is a well worn idea but compare that to a coach content to show up and deliver a lifeless, disconnected lesson. My goal during a lesson is for the other groups to see my folks having so much fun that they want to be part of that excitement.
When those two factors are in place, learning is much more likely since the students are actively engaged and interested.
Which leads to the idea that good decisions made by the coach are the key. Hurt folks, or bored ones are far less likely to buy into the learning process.