Reading the below guide explains quite well how to extend the network using powerline adapters.
The only thing that wasn't clear (to me anyway) was what happens with the wifi networks when you have multiple family zone boxes in the same house. For instance the first box creates 3 wifi networks. I add a 2nd box at the other end of the house (we have a loooong narrow house). Are the SSID's the same as the first box? As we walk from one end of the house will it seamlessly (as practical) switch from family zone box 1 to family zone box 2? Or am I going to end up with 6 different SSID's and the mobile device ends up picking the strongest signal?
If you have two Family Zone Boxes, they work like 'mesh networks'. If both boxes have the same SSID, the network will reconnect to the second box seamlessly. This will work so long as the SSID for both boxes are the same. The Box's load from the same configuration file that they retrieve from Portal which means they have the same SSID, so you will not see 6 SSID's in the house.
If you have further questions on this, please let me know.
Awesome :) Once I finish my testing and tweaking I will most likely be ordering a 2nd box.