Hello Laura Corbin,
Until you and the client know what he can handle, I suggest using seated machines that will act as a buffer to take care of any balance/energy issues. I am sure you and he have received doctor approval to exercise, as Karin mentions.
Start with two days of strength a week and three days of cardio a week at ten minute sessions at low intensity. Three days of flexibility and listen to the body; there will be strong and weak days. You want the person to leave the session inspired, not worn out, so they are able to continue on with their day.
Natalie aka NAPS 2 B Fit.
needless to say, you need a physician’s approval. I also assume that you do some form of assessment which you should do as for any other client.
Chemo may make him more tired as it progresses, in which case you will need to adjust the workouts. Since he has lost quite a bit of weight and has not exercised much lately (except for golf) I would start with a lot of stabilization exercises for core, hips and shoulders to lay a good foundation. I would recommend the initial goal to be one of strength endurance before increasing the weights to elicit hypertrophy.
As an experienced trainer, you should just follow your instincts and adjust the workouts as necessary.