I can imagine Bryan, I bet focusing was a challenge!
Why not ask them to help next timeMy neighbors thought it was hilarious watching me try to blow bubbles and get to my camera before the light breeze carried them away.
My suggestion, next time try a slower shutterspeed. At 1/125th, you're actually freezing the motion pretty well and thus losing the blurring affect that the panning/tracking is meant to give you. As an example, I have a panning shot among my vintage grand prix shots from a month or so ago. I had to crank the ISO down to 100, and the aperture up to f/22 to give myself a 1/10th sec exposure time to be able to pan with the car to get the background blurring that way. I know the photo isn't the best example of panning, but it gives the idea... you need a slower shutterspeed.
That said, the shot is nice, and as Dave pointed out, you exercised quick subject location and focus tracking very effectively.
Keep 'em coming! Nice capture. Though next time, find a child to help produce the bubbles for you...
Having an assistant would definitely make things easier .... but where's the fun in that