Don't design your workout program based on your age, design it based on your physical capabilities. Many people severely limit themselves as they believe they are too old, and this couldn't be further from the truth.
Here is a bit of what I did today with my client Evelyn over the course of her session. As I've mentioned before, she is in her late 50's and is extremely strong and fit. We have worked on her mobility, stability and strength, so training at this level is possible.
1) Goblet squats
2) Inverted rope climbs
3) Forward + reverse lunge combo
4) Advanced triceps push-ups
We did not do these in a circuit. These were just some of the exercises we did over the 60 minute session.