|From my experience its at around age 12 that parents start getting too annoying for me to continue coaching. 

Here's my speech to the parents on first day of practice.  

Hi, I'm the coach.  I've been doing this every year for 8 years.  I need 2 parents to help me coach.  If by the end of  my speech 2 parents don't offer to help. I'll recruit you.  My goal for the season is to teach your son the fundamentals of baseball and have enough fun so that he'll want to play again next year.  I get the kids to pay attention by bribing them, do any of your kids have any weird aversions to bubble gum?

Here's the paperwork for snack handout for after the game.  Who would like to take care of this?  After I hand this out, this is the last time I'm dealing with snacks.  

Here's the info for team pictures.

We've all seen the videos of out of control parents on kids baseball fields. I don't want to be in one of those videos.  I expect you to stay in your seats during the games.   

Unless your son is laying on his back in the middle of the field. DO NOT come onto the field.  

I have 3 kids.  I understand that a 2 hour break during practice can really free up your schedule.  That's fine, if you've got things to do, feel free to take off during practice.  Please let me know that you are leaving.  If you do leave. Please be back by the end of practice.  If you're not back by the end of practice, I will take your child home with me and you can pick him up from my house.   

If we can follow these rules, we'll get along great.  If you have any questions, feel free to call me anytime.  (I hand out my business cards). 

(I've been giving that same speech every year.)  

I've had 2 sets of parents banned from games. (9 yr old league)
I've taken at least 6 kids to my house to wait for his POS parents after practice.  (can you say parenting licenses?)

But I've never had one of them come onto the field.

But all in all, I love it.  

I've got 1 kid on the team this year, he's pretty athletic, but he's NEVER thrown a baseball or swung a bat.  So he's absolutely miserable right now.  But he wants to be good at it, you can see the determination in this kid as he's trying to figure it out.  Just in 2 practices, he's gotten significantly better.  That's what I love about it.  It's really infectious watching these kids get better, and getting excited about it.