Interacting with child objects from spawned prefab

Hi,
I´m really new to UNET and after hours of searching I´m not getting into solving my problem.
I´m spawning a prefab with a lot of child objects. Parts of them are disabled, because I want to enable them while the game is running.
I can enable (and see) them on client side, but it is not possible to make network calls on them, unless I click on "Spawn" in the NetworkIdentity component of this specific GameObject.
So, they have to be "observed". But how the hell I force them to be observed? I don´t want to spawn every single child of my prefab throu the server. Or do I have to?

After activating there is no NetworkID for this GameObject:


Here is the Spawn Button I´m talking about:


After I clicking it...


...my code for this Object is working:

Code (CSharp):

1. [SyncVar(hook = "OnTap")]
2.     bool isactive;
3.  
4.     void Start()
5.     {
6.         isactive = true;
7.     }
8.  
9.     [Command]
10.     public void CmdPickUp()
11.     {
12.         isactive = false;
13.         print("pickupServer");
14.     }
15.  
16.     void OnTap(bool enable)
17.     {
18.         gameObject.SetActive(enable);
19.     }

 

Additionally info: It is a non-player object.