David,
Try
this link. I'm not sure how much technical details you can pull out of in-cam jpg file, but if you're shooting in raw (either pef or dng) then you're definitely good to go.
Once again, the main idea here was that you might be tracking your son in AF.S (single, not continuous) mode having the shutter release button half-pressed with the distance between him and you changing. What happens here is, that camera focuses right when you do the half-press and then locks this focus position. This works if you do some panning on a static scene, but this is no way when shooting action. For the action tracking you need to set it to AF.C - continuous AF - mode (which is designed just for that), but I didn't shoot much in this one and thus have nothing to tell here, you can only refer to rfortson's experience.
Re focus-priority vs release-priority - that's apples vs oranges. In release-priority you may screw your shot up cause you were not in focus when you fully pressed the shutter release button. In focus-priority you can screw it up as well: if the scene is rapidly changing and/or it takes a long for the cam to focus (low light, low contrast scene, etc) then you'll end up with the shot that captured not that very scene you were hoping to get. I've set my K-5 for release-priority so I can control it - I mean I can get it 'somehow' or 'in any way' with immediate shutter release, or I can wait for the confirmation beep and then
push the pedal to the metal do the full click.
Zig
P.S.
Actually, if you need your camera for action-oriented photography, then Pentax isn't the best choice here. I'm not to say that Asahi-Pentax-Hoya is a definite failure here, but the system that you moved away from is much better with their predictable AF that shows its best at 3D tracking.