The voltage from an Arduino output pin drops as you draw more current.
I would not rely on this as a feature.
Secondly, it's much simpler/safer to control power to an item using a sink circuit (switching the circuit on the side facing ground) No voltage conversion needed if you use a 3V voltage source... (hint, you have one already) Note: The 3V pin on an UNO can supply about 150mA.
I always try to think of microcontroller pins as "logic level signals" and not as drivers. If I want a pin to drive (or control) something, I always try to design in something "sacrificial" to do the work. I'm much more comfortable sacrificing a 2 cent transistor than a MCU pin if I get sloppy on the solderless breadboard.