I'm in the "try to work with the neighbors" camp. Go to the parents and try to get them on your side. Don't go over raging about the kids, if you think you've got your momma bear up, think how those parents will react. Just be calm and reasonable and try to find some common ground. Maybe bring up the worry about the fence collapsing, that's a safety issue for the kids, as well as cost to them for repairs, as it is a common fence. If all else fails, enclose your duck yard so they can't throw things into it. Good luck.