Is This Safe Way to Power Arduino Slaves? (I2C Powering 2 Pro Minis Off of Uno)

[Potomac]

I have been playing around I2C with a master that is an Uno and 2 slaves that are Pro Minis

When I first started (and executed the communication code correctly), I was powering the rails on my breadboard feeding into the VCC pins of the minis with 5V from a benchtop supply. (See Method 1 in the picture below)

This is annoying and makes me have to sit next to the bench supply.

Is it safe to instead use the 5V pin on the master Uno to power the rails that feed into the VCC pins of the Pro Minis?  

In theory I think this should be fine, but I am not sure. Will it exceed the current limits?

See picture attached for visuals of what I'm trying to do

[rrinker]

 For a trivial test where the most you are doing is lighting up an LED, you should be ok. But what you REALLY should do is feed your power supply rails to the breadboard, and tap off there to the Vin and Gnd on the Uno and power the Uno from the bench supply along with the Minis, then everything is turned on and off with one switch, or just by disconnected one of the pins from the bench supply.