One more step you may want to take if you have many switches - power half from your "+" terminal on that rectifier, and the other half from the "-" terminal to keep the load balanced on the ZW and avoid sporadic whistle/horn operation on the tracks. If you switch to a separate transformer for switch power, this isn't as critical.
This will require you to switch the common legs of your LEDs(& resistor) powered by the "-" too, as the polarity they will see is reversed. If you are using a single bi-color LED, this won't work, so a separate power supply is recommended.
