Activating Child objects while parent object is already active?

I am trying to make a fire where if you hold a duplicate log over the fire it will catch fire as well. the log has all the same components as the logs in the fire and I think I know how to test the collision but I cant figure out how to specify what to activate and how to activate it. this is what I have so far.

(C#) public class FireSpread : MonoBehaviour {

void OnParticleCollision(GameObject other) {
	if (other.tag = Log) {
					var percent = Random.Range (1, 11);
					if (percent = 1) {
						
					}
			}
}

}

foreach(Transform obj in ParentObjTransform)
{
obj would contain a child , this would go through all the children of the ParentObjTransform
}

hope this helps for starters…