For flow, are you referring to transitioning from one exercise to the next? Sounds like you are doing that already with building on your combinations–that seems to me like it would flow better that way. Still trying to get at exactly what you are looking for…. However, you could try building on one combination, but before you are done, build another combination and go between the two for added mental stimulation (hope that made sense). Or, throw in a little “twist” to the combination that they are not expecting.
Guess I would need some specific combinations to give you better ideas! I do not teach Silver Sneakers but I am familiar with it (some day I plan to teach it–I filled in for someone once and loved the group).