Schedule wise you can usually go whenever you want, as these people tend to be retired and have plenty of time.
These classes are certifications given out by the Silver Sneakers program. There are several to choose from, but none are high intensity or advanced.
Because you’d be working with a large number of geriatric-style clients, you must ensure that all of the exercises are easy and safe. Many of these people have been inactive for years.
You won’t actually be teaching through Silver Sneakers though. You are certified to work with their members, and the health club reimburses you.