I will say this - I live in Ankeny and I was really concerned about parents even for rec leagues. I've had a great experience with parents. Never had one issue. Every year I've been praised universally by parents for coaching baseball and let me assure you I was the worst baseball player on my team every dang year growing up. Some of it is on the coaches too - I communicate exactly what I'm going to be doing every year with our open time. I'll take suggestions and help but that's it. If parents want to directly contradict what I'm trying to do at that point, I'll offer to let them coach the team.
I've coached my kids' teams in different sports for years, and can't say I've ever really had a problem. With my daughter's teams, it seems like parents are just so thrilled that someone is willing to volunteer to coach girls sports that they aren't about to rock the boat. The closest thing to an issue I've ever had is parents that think their kid can never touch a ball outside of the organized practice all year long and assume I'm not doing a very good job because their kid struggles.
And with the boys teams I've pretty much followed the - if you show up to practice, work hard, have a good attitude and are a good teammate you are going to play approach. And if I have an issue that is going to cost a kid playing time, I give the parent a heads up ahead of time and share the details. In some cases like a kid that can't catch wanting to play 1B, I have to tell parents that we'll work on it in practice, but we have safety considerations to think about, as well as trying to put kids in positions where they can push the limits of their skills while still giving them a good chance to be successful.
On the other side as a parent the only issues I've ever had is when the coaches communicate something like I said above, then pull some douchery that sends mixed messages or embarrasses kids. My prime example is in basketball, where there's been one player that is really good, and the rest of the kids are all decent, but a notch below that kid. A coach makes sure his kid is always playing with the star player so he can pull the "That group was playing really well so I wanted to stick with them" excuse while other kids that are as good or better, and more importantly are good kids, teammates and give effort, ride the pine. But overall, those types of things have been rare, and pretty much everybody coaching my kids' teams have done a good job and deserve a lot of slack.