How do I send an event to a target and all of its children?

I created a custom event type that I intend to use to inform my controller input that the user is interacting with the UI, and not to process input.

 public interface IProcessInputHandler : IEventSystemHandler {
     void OnDisableInput();
     void OnEnableInput();
 }

I applied this to a script that is a component of a GameObject. This GameObject has a child object that is the player camera. This player camera also has a MonoBehaviour script that inherits this same interface.

 public class Player : MonoBehaviour, IProcessInputHandler {
     //Implemented.
 }
 
 public class PlayerCamera: MonoBehaviour, IProcessInputHandler {
     //Implemented.
 }

I used the static helper class ExecuteEvents to execute the event in the EventSystem:

 ExecuteEvents.Execute<IProcessInputHandler>(player, null, (x, y) => x.OnDisableInput());

As expected, this gets called on the Player GameObject just fine. It doesn't get called on the child GameObject PlayerCamera.

The manual suggested that there was a static function on the helper that could do this.

I only found ExecuteHierarchy which executes up the hierarchy. Sure, I could execute from PlayerCamera up to Player, but that's not the behavior I want. I want to execute to Player, then to Player's children.

Is my only option to use SendMessage, or am I just not using the EventSystem correctly?