I would think it would be full body exercises because you are covering the entire body but I'm not too sure. I can't really see how it would help your immune system because the immune system is what protects your body from disease, virus, etc...
B. Hormones control the bodies function such as metabolism, sexual development and growth.
Answer: Hello! It all depends on your take and his health stats. If you think he will be able to handle it then youd explain it in better detail. Answer any questions he may have. If you think he should wait a bit, still tell him what it is and explain to him why you think ot is best to wait.
Good luck babe!