Jim;
I've looked at this image several times since you posted it, trying to concisely decompose what I find rather captivating about it. Here's what I've concluded.
1. Gesture and expression. That subtle head tilt and Rowan's solemn, actually rather stern, expression are eye-stoppers. As I see the midday sun I realize he's squinting in the glare. But it seems that he wants to be somewhere else and grandpa is being a pain in his ass with the camera. It's excellent.
2. Nose Band-Aid. Just a touch of mystery, even to grandpa.
3. Big head. That 90-degree pose, Rowan's small upper body and his protruding ears make his head appear just slightly abnormally large. This accentuates the effect in #1.
4. Dark shirt. A white tee blasting fill up wouldn't work as well. I must say, however, that I'd consider cropping the shirt's chest design. Maybe, maybe not. Not sure myself.
5. Soft focus. It's slightly distracting but in this case it creates a feeling between candid and formal.
Nicely done.