For a team, a lot of great info posted above. I'd also add that you highly recommend that the parents work with the kids throughout the week. Most won't because they don't care, but some will and you'll notice a huge improvement with those kids.
If it's ever for your individual child,...hitting coach. As much as you don't want to hear it, it really is the best option.
My daughter has been playing softball since she was 5, and she is pretty good. We worked with her on her swing, but her form was so inconsistent and she fought us on almost everything (kids do that with parents), but we're also hard headed and kept trying, especially since my MIL was a HS softball coach. We bit the bullet for hitting lessons and it has made a world of difference. He broke down everything for her all the way down to how she holds the bat as she walks to the plate. Feet, hips, hands, elbow, etc. He starts her on a tee that he sets up to work on outside pitches, then sets it up for inside, and he watches her form. Feedback with every swing. Then he moves to pitching her from pretty close and working on her seeing the ball out of the pitcher's hand, identifying balls/strikes, and her timing (fast, slow, inside, outside, etc). She's been going to him for a few months and it's night and day on her consistency as well as power. My son is 7 and has his first lesson today, so I'm pretty excited since he's one where sports just comes natural to him while his sister loves sports but it takes longer to "click."
When she told us she wanted to pitch as she was moving up to 10U kid pitch, we didn't even try to work with her. We just went straight to lessons with a well known pitching coach in our area and she's responded very well. In her last tournament, she went 2 innings with zero contact, 3 walks, and 5 strikeouts. She also hit a bases clearing triple that one hopped to the fence. Not bad for 9.
You also have to practice. She pitches to us 3-4x per week where we focus on the adjustments that her pitching coach did in the previous lesson, and she hits 2-3x per week. It helps my inlaws are huge sports people who sent 2 of their 3 to be collegiate athletes, and my FIL built a batting cage in his backyard and bought a Juggs machine. I asked him why he was doing it, and his response was pretty simple..."it's cheaper than a lawyer."