LED power supply design / lay-out
Okay I now have enough information to answer. To put it simply, the fewer power supplies you have the better. It is better to have one power supply that can deal with the highest current needs than it is to have two power supplies, one for logic and another for the LEDs. The only time this isn't true is when the two power supplies are internally connected. I.E.- you have a power supply that can provide both 15A @ 5V and 800mA @ 3.3V. Fewer parts is always better plus routing AC cables to all the supplies would be horrifying from a safety perspective.

Yes, that's a star ground. Yes, that's exactly how you do it, though to be honest, star grounding doesn't help the digital circuits, ground planes do better to absorb switching noise form the transistors. 

Other thoughts: If you only need to have all LEDs on for a few seconds or less, you could get away with a lower current power supply and buffer the needed current with capacitors. An example: You have 3 10W LEDs (for simplicity). If they are ever one at the same time, they are only ever on for 2 seconds together before one of them switches off. You can't have the 5V line droop below 4.7V before somethings blows up (for simplicity, not actuality). You could potentially buffer the current draw by adding a 1334F capacitor (not realistic). You get that from E = 0.5*C*(V^2) where V is the change in the voltage you can accept, c is capacitance and e is the energy, which we got from 3*10W for 2 seconds (3*10*2=60J). That's just a thought exercise, I don't know your timing. But, if the concept works out to where you can buffer the current draw with a capacitor, you size the power supply based on how fast you need to recharge that capacitor and not on how much instantaneous current draw you have.