When shooting children, try to get on their level. I usually try not to shoot down on them, it makes them look smaller than they are. When you're shooting at the same level, it really brings out their personality.
I would also try not to use such a wide aperture. It's already been mentioned, but the first photo is a throw away for me. All the wrong things are in focus. I don't like the flower in the corner of the second one. It doesn't add anything to the photo and looks out of place. I would try cropping it just under his hands to take out the flower and shoes. It might work, it might not, but I think his expression is good. The last one could have worked if the boy was farther away from his parents. It looks really strange since he's right in front of them and they're blurred- like it was done in Photoshop or something.
It's a good start, though! Keep practicing!