For me there are two ways to look at this.
Way number one, if I need clients, I go with a very reasonable rate of $10 each per session. Each client pays for “x” number of sessions up front. Missed sessions are lost sessions. It is an excellent price point, no bending over backwards to make up sessions. Sessions could be rescheduled 48 hours in advance. The great price will give them a second reason to recommend you. The first reason will be that you are a great trainer, who makes working out fun. In this situation I would also schedule the sessions to make the clients happier. I am building a clientel. I can control scheduling more when I have a strong business.
Way number two, I don’t really need more clients. I go with $20 – $25 per cient per session, same set up. But maybe I cut the reschedule to 24 hours in advance. If I don’t need more clients, I kind of like the occasional dropped session so I can have some extra family or me time. In this scenario, I schedule the sessions at the start or end of my schedule for the days of the sessions. No prime time for a group unless it is agreed that there is no refund/reschedule. Groups this size reschedule more than private sessions and duos/trios.