Just wanted to report back on how it went today. It was a beautiful day, mid-50s and bright fall sunshine. We headed out and Izzy was really excited. She isn't ridden outside often and she thought this was just glorious; ears pricked, bright eyed, and a big bounce in her step.
It quickly became obvious that our primary goal for our ride was getting her to pay attention to me when she was so excited. Cars, wind, falling leaves, all of these things were very interesting to her. She wasn't dangerous/out of control, just very stimulated by all the new sights and smells (she gets lots of turnout, but on the other side of the property- this was new scenery for her). In fact, there was a lot of shooting in the mid-distance, and that didn't seem to catch her attention at all- she was more interested in the leaves falling around us.
After I got her paying attention to me, the next big issue was tempo. She is usually a forward type (we like to call her a sporty Morgan :) ) but she was borderline too quick today (i.e., I asked for a trot and she immediately wanted to canter and was hard to bring back down). So, we focused on walking, spiraling circles, direction changes through the circle, etc. The little, important things. I would say we probably rode for about 40 minutes. She worked up quite a sweat during that time and took awhile to cool out.
All in all, it was GREAT to get outside into the fresh air. Given all the concerns about putting too much strain on her legs, and the "rushy" way she was moving, I don't think this is something I will do regularly, but I did enjoy feeling the sun on my face today.
Thanks again for all the advice and suggestions.