Discuss your issue with the children's parents. If you know the children who are destroying your property, visit their parents and explain the problem. It's possible that informing the parents will solve the problem altogether, and it's also possible that you'll get financially reimbursed for the destroyed property. When talking to the parents, ensure they understand that the children are not to enter your property. Politely mention that you're going to take further action if property is again destroyed.
Contact law enforcement or the non-emergency number to the police department and voice a complaint. Seek advice from a police officer and request that he make frequent drive-by visits near your house or property to ward off any issues from youth or teens. It may be necessary to get a restraining order banning youth from your yard. Understand, though, this is difficult if you aren't sure who's destroying your property.
Establish a neighborhood watch group and make it a mission to increase neighborhood safety and crime prevention. Invite your neighbors to a meeting and, as a group, discuss issues and needs of improvement in your neighborhood. Mention that youth have damaged your property. Discuss with your neighbors ways for residents to stop this behavior. Stress the importance of everyone working together to look out for each other's children and property.