Hi Josh,
Another heart-warming picture, well done.
In this specific case; I think the expression on your son's face makes this work even with the dog being
so out of focus, although Manfred's point is valid.
It occurs to me that if you were to re-shoot the same scene with a view to getting a better version simply using a narrower aperture, say f/11 instead of f/3.2, that might still not achieve all we'd like.
Assuming camera is Canon APS-C (and using that 50mm lens), the Depth of Field (at 3 feet shooting distance) is only about 2 inches at f/3.2, this grows to something over 6 inches at f/11,
but to make the most of that,
you'd need to set focus at a point in space between your son and the dog.
If you just focus on your son's face (and use say f/11), because of the way Depth of Field 'works', you'll get a sharper background too, which is no benefit whatsoever, and only a slightly sharper dog.
How do you focus on a 'point in space'?
a) AF on your son, then give a small manual adjustment to the focus ring, or
b) AF on your son, hold that focus distance, then physically move yourself (and camera) slightly further back by an amount that equals approx. half the distance between your son and the dog
b) is a variation on the 'focus and recompose' technique
You may need to experiment with settings* to get the best from these techniques, especially with moving subjects and fleeting moments - but from what we've seen, you're doing well.
* there are other camera settings that may defeat what we're trying to achieve here
Of course, iso and/or flash power will need to be increased to maintain the correct exposure while using that narrower aperture.
While my assumptions and figures may be out (by some margin), I hope the general principles help you achieve a better result when DoF
really matters (e.g. shooting at close quarters, as you are here).
Good luck, Dave