First of all get a solid lens with an opening of 2.8 or better. More light is more speed is sharper photos. Use a monopod to balance the camera and lens. Position yourself in that way the play comes to you, that way you have more time to focus. Shooting from the sides is asking for trouble unless the pass is going for the other side of the net sideways in your direction. Choose low angles so you can catch them mid air and use the added height in the photo, makes it more spectacular. All in all, don’t give up and keep trying.

50 mm 1.8 or something like that works well inside to shoot with.

Yep, didn’t think of that since the photography I do is mainly for me and rarely for other people.

Personally I think most of the shots look like snapshots everybody with a camera phone could have made. I would like to see more bokeh and more cropping on the rule of thirds. But i assume that is your style and they agreed to that before the session. I think posing wasn’t great but not bad either. I mean you do see the fun and love they have in the photos and I think that’s what it is all about. Either way, can’t please everybody. If you’re going to do a second shoot I would suggest splitting the costs with them and let them tell you what they think should be different in that shoot. or tell them to piss off because that is what it is.