I have to disagree with Chad
a bit on this one.
You can easily use 5v from USB for the LEDs as long as you don't exceed 100 mA for an unpowered hub port or 500 mA for a powered/dedicated port
or use the molex for 5v and/or 12v depending on the voltage/amperage requirements of the contactors/shakers/flashers you use.
I use 12v LED buttons from Paradise with a 5v USB power tap.
You can light 14 buttons and a 3-LED trackball drawing only 81 mA -- example
here.
For your setup, you won't even need resistor R2.
Scott