I would like to have a common rail of ground to which to clamp each individual ground, including the source one ("Thunderstuk").
Because I want to show all these items to children, I am now allowed by law to use PCBs.
WARNING: Failure to securely seat the connector may cause electric shock, short, or start a fire, and lead to serious injury, death, or damage to property.
Use lead-free solder on your PCBs. Then it is safer for the kids.