Don't worry about being the only man (you probably won't be). I go to a couple of classes each week and there have been men in both. Pilates is really good for keeping us strong, supple and fit, just check out the instructor, I prefer one with a physio background. Instructor should also get you to do a proper medical form so they know about anything that might be an issue and will adapt exercises for you if you have a particular injury or difficulty. I'm mid 70's and recently spent two weeks in hospital following a riding accident. Most of the nurses etc commented on my physical strength and it really helped with my recovery. Good luck with finding a good class and enjoy.