With all devices at 3.3V things get easier.
Firstly, wire everything up and check what the maximum current is drawn by the chips
(while idle, while measuring, while SPI transfer).
If it is small enough, you might even get away with powering the chips directly from one or more of output pins
(the same way you would power up an LED).
A more reliable way is to use a mosfet or transistor from this kit:
I would try P-channel low-Vgs MOSFET, similar to: Learn And Build A High Side Switch | Hackaday
It is easy to understand how it works, and you can try to light up an LED+resistor with it first.
But make sure you are not accidentally sending power or providing ground through the SPI pins! Turn SPI off
when done and put the pins into INPUT state.