Hi Amanda, and welcome to TPF!
As far as this shot goes, I quite like the pose of your son and his focus on the dandelion. I will take a different viewpoint from Designer and say that, for this particular shot, not seeing his eyes seems quite natural, given what he is doing. You already mentioned the fence in the background - again, it's a casual backyard shot, so that's fine for this setting. But if you were shooting for clients, you'd want to scout out an area and be careful not to include distractions like this.
The real issue with this image is that you missed the focus here. Unfortunately, the sharpest point in the frame is at the top of your son's tee shirt, not right on his eyes. Closed or not, the eyes are everything in portraiture, especially in close crop like this (which I like here).
Keep practicing - a little fine tuning and this shot could be a real winner! He's a cute little boy.
Please keep posting your work - be sure to check out our Galleries section, where you'll get more views and feedback. Enjoy the forum!