I agree 100% with what IHF said. Perfect example of constructive criticism. You do have potential. Just follow some of those tips. I also love shallow DOF with my 70-200 f/2.8. But remember, that aperture doesn’t have to stay at 2.8! The photo with the one boy’s face completely out of focus just doesn’t work that way. The subject of that photo was solely the one in focus, the face of the other creates visual tension and distracts from the other. Usually when shooting portraits of multiple people, you should keep all of them in focus. I’ve seen lots of the groom in focus, bride walking up behind not in focus shots… those seem to work for the most part, when done and composed right. But it’s the visual tension that ruins your photo. I love the one of the boy walking, but I agree, place him on the rule of thirds and it would be a much stronger image. Your white balance is just a bit too orange. It’s not horrible. Even if it’s not pop-up flash it’s too intense in some of the images. A diffuser may help. I however prefer using natural light, even on slightly overcast days. Fill flash works best for me outdoors when it’s a sunny day and you don’t want to blow out the sky. Practice with that idea in mind. You can shoot without any flash on an overcast day, just bump up the ISO and maybe use reflectors pointed up at the subjects’ faces.
Keep practicing, as long as you do you can be very successful.