Walter Scott’s family plans to file a lawsuit (a wrongful death and civil rights violation lawsuit) against the city of North Charleston, its police department and police officer Michael Slager, who fatally shot Scott while he was running away from the officer.
Notice that the officer is being sued. Notice that the officer, after being charged with murder, is assumed to have acted with malice.
You are trying to compare 2 different things. If you think a police department would be sued because the officer let 2 kids play in a park, you're being dishonest or don't understand the law. So again, the parents would have no standing to sue anyone in this scenario. I've already reference the relevant MD statute and Supreme Court Decisions.