plugging in two PIP's in one socket

Each PIP draws 12 Amps, so it will blow the breaker even if you used a dedicated 20 Amp circuit.

 

since the maximum current draw is 12A per vehicle, 2 of them together could possibly add up to 24A, that's most likely to blow even a 20A circuit breaker, depending on many factors (ambient temperature, age/condition of circuit breakers, voltage drop etc)

if you had a 30A 120V circuit (not likely to be found), it would work.

usually found at RV parks, "TT-30"'s, that are 30A 120V outlets, you could plug 2 PiPs into one of those, with a TT-30 to standard outlet adapter and a splitter... thats about the only case I can think of where it would work.

this link has a picture of a TT-30 to standard outlet adapter

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Plugging them in is not a problem. Charging at the same time would be. But if you use the delayed charging feature you should be able to charge them both overnight..

 

It is a good idea! To be on the safe side, you can set one car's timer to an End time which is before the other car's Start time.