Any feedback on structure for outdoor group walking programs for seniors (time goal) and for distance goals??

I am diving into more group programming, and group walking programs would fit my client's needs. I am curious of what sorts of structure trainers have found most successful in managing walking with groups (to handle different fitness levels, speeds, etc)? I am looking at senor-specific, as well as a separate class for any age. I plan to walk with the group. Walking programs incorporating use of bands for strengthening is also an interest.