Hi Tecmec,
This is NOT possible. An End Device is a Reduced functionality device (look in 802.15.4 spec for more info) It ONLY has the capability to communicate to its parent. the Parent must handle the routing.
A Router or coordinator can communicate directly to another device within its hearing range, if it creates a mesh route first.
Using a broadcast address will make the End device send a packet to its parent, which then will handle the broadcasting to the rest of the network.
BR,
Mads