I too wish that C2 took a more OOP approach, but it's not likely to happen due to C2's architecture. Perhaps C3 will, but I doubt it considering Construct's target audience, and the fact that C2 projects will work in C3.
Fortunately in this scenario, the workaround in C2 isn't onerous. If you add all objects to a family, add a "Parent UID" instance variable, and use it to populate each object's parent, you can destroy all children with just 2 events: