I know it's always one of my top priorities to make sure I'm 'safe' from the likes of childminders whenever I move into a property :) Lol
Maybe you should simply speak with her, non confrontationally, and explain that the horn beeping is ticking you off nd ask her if she could please ensure that people dropping off and picking up cause minimal disruption?
She's a child minder, not Hanibal Lechter, do you really want to cause her all of the very real grief that you will if you shut her down down, even if it's possible?
If you do then maybe suggest she moves, I'm sure she'd love to under the circumstances, because frankly I can't see that she's doing anything wrong, other than not signing on, trying to work honestly and paying her own way.
You don't want people like that living next door to you do you?;-)