I don't really know why you are having that delay and the message received is broken, but the broadcast message is the best solution to achieve what you want.
If you are using ZigBee modules, remember that one of them must be the coordinator and the rest can be routers or end devices. To change the role of an XBee you have to update its firmware.
Once you have a coordinator and other routers/end devices, all of these have to be in the same network, so their ID and SC settings must be the same.
To send a broadcast message, the DH setting of the sender should be 0 and the DL should be FFFF. With this configuration and working in transparent mode, what you write in the console of the sender will be sent to all devices on the same network.
Hope this helps.