Getting Bounding box from a collider with children

hi there my friends , ok here is my problem: i have an empty game object and it have a lot of child objects (its a room) i want when i hover my mouse at it , it gets highlighted by the bounding box of the room , the problem is the empty game object does not have a renderer or anything else , only a collider its like this:

MeeteingRoom (empty game object that have only a box collider)
otherobjects (the models themselfs)
.....
.....
.....

the code for mouse hover is done and working fine , but how i could highlight the whole object is still not working , i was thinking of using mesh.bounds but the empty game object dont have a mesh (it must not have mesh).

on the other hand , i tried the following code:

 var roomObjects : GameObject;
 var highlightmat : Material;
 var selectedObject : GameObject;
 
 function Update(){
  var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
  var hit : RaycastHit;
  if (Physics.Raycast (ray, hit, 500)) {
  Debug.DrawLine (ray.origin, hit.point);
  if(hit.collider.tag == ("Rooms")){
  Debug.Log(hit.collider.gameObject);
  selectedObject = hit.transform.gameObject;
  //isHighlighted();
  }else{
  Debug.Log("Notting!!");
  selectedObject = null;
  //NotHighlighted();
  }
  }
 }
 
 function isHighlighted(){
 
 }
 
 function NotHighlighted(){
  
 }
 
 function OnPostRender()
 {
  if( selectedObject == null )
  return;
  
  var go = selectedObject;
  highlightmat.SetPass( 0 );
  var meshes = go.GetComponentsInChildren(MeshFilter);
  for( var m : MeshFilter in meshes )
  {
  Graphics.DrawMeshNow( m.sharedMesh, m.transform.position, m.transform.rotation );
  }
 }

it works great but the scale is wrong bcz the importer scales the imported objects from 1.0 to 2.54 , how can i take the scale and add it to the above script?

thanks for any help i get.