You're getting some great expressions and fun pictures. I'd try to be more aware of the backgrounds and vantage points.
Before they start playing in the water (or whatever wherever you're going), figure out where to stand in relation to the water and notice the background and adjust your vantage point as needed. If someone walks thru your shot wail til they get out of the frame (and if they're taking their good ol' time you might need to take a step or scrunch down a little to get them out of the frame).
You're maybe rather tall and need to frame a little lower so you're not getting stuff along the top edge of the photo that doesn't add anything to the picture and so you're not cutting off the subjects. For example, the girl's hand is out of the frame in #4 and if you'd flipped the camera vertically you could've gotten more of her; also if you'd moved a little to your left you could've kept that orange trash can/porta potty out of the frame. (Even if the background is less in focus it creates a bright orange blob that's visually distracting.)
Just takes lots of practice and being aware of everything in the frame. Also with sports and action it can help to be set up in a good place so you can anticipate something happening (like kids + water + a hot day means playing in the water! lol).