Dil to yehi karta hey par what if that is just a 7 year old boy :(. I have had this experience many times as in front of my house is Christian basti and their kids are "well Allah knows what kind of they are". But I could not do more rather than just serving him with a tight slap on his face :(.
The best way to avoid this massacre of car paint I found is I cover her all the time with cloth, they still do cher char with cloth, but at least car is safe. Be it dirty, put the cloth for the sake of preventing this bullsh$t.