you did not mention whether you work with the clients one-on-one or in a group which makes a world of difference because one-on-one you can evaluate the individual and do a program based on your assessment. As you well know, there is hardly an age group as diverse in abilities as the one you have been defining.
I am not sure whether there are any new ideas I have to offer. Your Pilates certification certainly would have given appropriate modifications for a group where you have to be concerned about osteoporosis, and if you teach this as a group, I would modify for the entire class accordingly.
Working with adults in that age group myself, I noticed a difference in self-perception, particularly in the lower end of your defined age range. I am observing greater confidence in their bodies’ abilities because we are encountering a generation that has already exercised in their youth and maybe with Jane Fonda. They do not want to be treated as ‘older population’, and the language we use needs to reflect that.