Dogmamma, I think my experience might help. We are the same age. I had originally intended to quit teaching (i.e. take my retirement $ and invest it myself) when my younger son graduated college. After he quit school and joined the Marines, I decided I would still quit 3 years later. It had been years since we needed my salary (which was very good) to live on, and we were using it to build our retirement and pay for college. I was interested in the same things as you. I even bought the study guide to take the ACE personal trainer exam. I wasted a lot of $! Even though I was a certified ACE group fitness instructor, I had let that lapse and the materials seemed daunting. So, I kept teaching and then I did just quit. That didn't turn out so well. I envisioned riding all of the time, but I didn't. All of my friends work and I've done my time with volunteer work, except for the stuff I do for AMC, which is mostly leading rides. I considered many quasi medical fields, but frankly, I have no science background or aptitude and I couldn't face taking chemistry, and other undergrad courses before applying to grad school. Heck, I already had an MA + 90 credits, as I was a PhD drop out, as well as a CAGS (post master's cert. for teachers) drop out. So, I went back and thought about what I really wanted to do when I was in college, which was to be a therapist. I didn't want to get a PhD, so I looked at 2 different degrees, clinical mental health counseling and social work. They have different routes to get to the same end, but I chose the clinical mental health counseling for two reasons. First, I wanted to do clinical work, not case work. Social workers get out with a masters, and then need to do various certifications to get licensed and to practice independently. Mental health counselors (and this varies by state), take the licensing exam right after they graduate and then can work, but with restrictions, until you get a certain number of hours. Of course MA has the strictest rules. We take the exam and then have to do the equivalent of 2 years full time work and then you are fully licensed, with privileges to practice alone.
I then had to decide where to go to school. I chose the expensive private university with a 3 year program over U Mass Boston, with a 2 year program, because I knew right away it was right for me. There were a good number of older students (we had a "club") who were career changers. And the majority of the students were in their 30s, not right out of college. I've been working for 1 year and 3 months, for a large social service agency, in their community mental health clinic. I will be taking my exam in a few weeks and I will have my hours at the end of June. I love my career, but it is very hard. You can't take it home with you. I had already learned that, in teaching, so it's not an issue for me. Self care is a must. And, I make my own schedule. I work 80% time and I will have plenty of hours... have free time during the week. Age is not seen as a detriment, from what I experienced in interviewing. I will be frank and say that being fit and looking a bit younger helps. I talked to the head of career services at my school and she was honest and said you don't look old or dress old and in this field experience is seen as wisdom.
Once I get my license, I will drop down to 2 days a week and I plan to work on the ACSM certification in wellness counseling and do that as my own thing on the side. There's enough desperate older, well off people who are willing to pay for this, with no insurance. I can keep my clinical skills up by working at an agency, as there's no way I want a full private practice.