if the marauders were brilliant enough to discuss their fullmoon trips in front of snape, then there’s no way they’d be able to conceal themselves from mcgonagall.
unless of course some things would just be too much for her to handle.
a mood
I mean, its 100% a potter mindest to think “Okay Im giong to need to be stealthy about this and sneak out of the castle each month. Clearly the best way to do that is to become a large stag with conspicuous antlers”