Hi Michael,
Having experienced the challenge of photographing your own child (who you note cannot stand still for more than 0.00001 of a second) it is perhaps no wonder that most parents simply give up and employ child portrait photographer instead to capture images of their child. Trying to catch a good photograph of a 2-year-old on the move is never an easy task.
That being said, there are some techniques you can employ to help stack of cards in your favour. One simple option is just to let the child get on with exploring their environment. Then, all you need to do to is stay nearby with a telephoto lens and rely on capturing the moments as you see them. What you need to get good at though, is keeping your camera to your eye and keeping the subject in focus. Then you just need to be ready for the moment.
I think the lighting in the photograph is really good; using backlighting is a common professional technique. About the only thing that I do not like is the sight of those nappy… I am not a parent but my hunch is there is a surprise waiting there for someone!
Keep working on the technique – you’re going well!
Cheers, Anthony.