Ever since I started teaching strength and movement, I have included play components in personal training and in our small group class programming ... and of course in my own training. I refer to this as Fitness Freedom.
We all need time to explore, learn, be free from reps, sets, time and be allowed to challenge our bodies in new and different ways.
Any movement or lift can be considered a play component -- Fitness Freedom has less structure and allows the individual to make decisions about whether to push forward or pull back.
It needs to be safe, fun, and even a little bit challenging. It may be different than our typical gym programming or it may build on what we do every day.
So much is gained from play: besides strength and conditioning ... there is confidence and excitement, in addition to the opportunity to develop (or improve) skills.
Give it a try and let me know how it goes!