The first thing you can possibly do when beginning a bootcamp is warm your clients up with simple movements. Have them do high knees from one area to the next, light jogs, sprints, but kickers…etc… This will help give you a feel for your clients athletic ability. Once you have an idea of how in shape and athletic the majority of your clients are it is easier to come up with more complex and challenging movements for the whole group. It has always helped me to carry a paper of exercises I jotted down to help refresh my memory if I became stuck. Always be in control and confident when conducting and demonstrating exercises. People love a little humor at a serious time as well. If you stay friendly and confident at the same time there will always be returning clients as well as new ones.
Best of luck