On many shots, but not all, I would really think about turning the camera, to shoot "talls".
The two shots of the little girls for example, really do not work well as horizontal compositions, and in the second shot, the one where she's sitting in the chair, you have her looking right out of the frame...if you absolutely must frame a shot like that as a horizontal, it's better to give the subject some room to, as they say, "look into".
Photographing small children in the vertical or "portrait" camera orientation makes the kids' heads larger, faces clearer, and also allows the moms and grandma's to see the cute little outfits that they worked so hard to buy, pick out, or have saved for decades to dress the little ones up in...
A horizontal framing of a small child, like the boy in shot #2 makes him small in the frame, cuts off his arms and torso, and shows us 50% of the frame with the boy, and 50% of basically black, uninteresting dirt behind him....there's no reason for the horizontal camera orientation in shot #2.
Shot #1 is a different story--in #1 he is seated on a playground slide, and the picture is "wider than it is tall". That makes sense as a horizontal, but cutting off his hand and his head are kind of less than ideal framing choices. Same with the cut-off foot in the last shot of the boy in the red wooden chair.
Shot #3 she has on a cute blue sundress that her mom or grandma probably bought her...but we cannot see it...and the yellow flower is competing with her...a tall framing would have emphasized her cute outfit, her, and minimized the competition from the background and that honkin' yellow flower...same with #3..the brickwork in the background is bright..."light advances, dark recedes", meaning that the bright highlights on that chimney "advance", subconsciously, out of that mostly dark background,and visually draw the eye away from the main subject, so always watch out for bright,overexposed elements in the background.
I hope some of these ideas help you in photographing kids!