When I was selling my horse, I would ask for a phone call. I would get calls from people wanting him for their 8 year old (Haha..no) or a 16 year old looking for a highschool rodeo horse. A lot of the times, I would get emails like:
"Your horse is very pretty. Does he buck or rear?"
"Can I have pictures (when there were already four or five up)"
"I will take him"
I would ask for a phone call because I think if you want to purchase my horse, you should be able to MAKE time to call me (I answer my phone whenever). Like CDT said, it gets rid of the people just window shopping with no real intentions to buy.
My adds were very informative and I would reply back answering any questions with "Call me at x to discuss further". I think that is fair. You have issues with your children, I have issues with answering 10,000 emails that probably won't lead anywhere.
Just a POV from the other side.