Maybe just in the child's room then, also you might want to ground that Faraday cage if they have anything that could be transmitting WiFi or Bluetooth or even is just a large screen.

Also it needs to be a fine mesh because for blocking 5GHz WiFi you want the hole size to be a 1/20 of the wavelength which comes out to >4mm.

Or an even cheaper solution would be to get one of those large "pet" cages and run a wire straight into the earth hole of a power socket.