Call the police. File reports. Take pictures of the scene. Evidence is so important here. You could absolutely at the very least sue for emotional distress for your loss.

The parents should have been watching, that being said sadly kids make mistakes. Do you think it was done intentionally to harm your dog? The thing is at the age under 10 they very easily could have not known and their parents could have just thought they were playing outside. That does not mean that they are exempt from any responsibility, it was them not watching/ teaching their kids not to feed animals candy that is the cause of this and it is up to you to decide if you want to take legal action. If you choose to do so, small claims is your best bet.

That being said, I hope you're doing okay op! It's really sad that this happened to you.