Hi There! I'm new to the Forum, too, and figured that this post might be the best one for me to jump in and say hi! In my 40s, too- but not new to horses.
Max turned 18 yesterday. We've had him for 11 years, but only connected with the mini world about a year and a half ago. Believe it or not, he was our riding horse for my daughter, starting when she was three. She was always tiny for her age, so she got to ride him until she was about 11, and then we trained him to drive. I know that very few people use minis for riding, but Max is pretty big- 37 inches and about 300 pounds, so he's stronger than the little guys are. He loves trails and jumping (yes, my daughter learned to jump on him).
We started showing him last summer in jumping, hunter, and obstacle. My daughter hopes to show him in driving cones or driving obstacle.