I would not make the exercise selection dependent on the perception of what a 50+ group cannot do. Somebody in that age category signing up for “Boot Camp” is not likely a novice exerciser or a frail little old lady.
You can modify any exercise up or down as the need presents itself. The one thing I would avoid, though, at least initially until I get to know the group, are fast directional changes because many people do not train like that by themselves, and the body may not prepared for it. After all, in a class setting, people are more likely to overdo things because of perception of peer pressure or competition.