Well, I ended up using wide tracking in continuous, setting 5. While shooting, I thought for sure I must be missing a lot of shots, as the green squares always seemed a little behind the subject.
As it turns out, this was entirely wrong. It seems the display of the AF points is just not quick enough to keep up with what the camera is actually doing. I was shooting with the 50-230, not known to be an especially fast focusing lens, and my keeper rate turned out to be quite good. I had very few frames where the AF didn’t grab the subject and stay with. I’m actually pretty impressed.