voltage drop across collector and emitter when using transistor as a switch
Generally speaking, when you wish to use an NPN transistor as a switch, the emitter should be grounded and the load is connected to the collector side of the transistor. In your case, ground the emitter and place a 220 ohm resistor in series with the collector to your supply and then connect the Pi's to the junction of the resistor and collector.

You are showing a resistor in parallel wth the Pi's. This should be removed.

You didn't state what input of the Pi's this is going to but be aware that if combined they represent too much of a load, you may have to use more than one transistor circuit and split the Pi's among them. Test your circuit with one Pi first and then add others.

Also take note that an NPN in this configuration will invert your logic. When the base is biased on, the voltage to the Pi's will be low (about 0.2 volts) and vise versa.