It might be controversial but they seem to be going about this the right way

Their kid is at an age where they'll learn about genitals and if I read this right both people in this relationship are non binary/female presenting so they probably both go by some form of mom or mother and while they used to refer to their genitals in a casual, crass way they now need child appropriate language to explain genitals with their kid, they can't just say mommy has a pee pee since kids are precocious and if they happen to say that to their grandparents or a stranger that would raise an eyebrow and probably start an uncomfortable conversation, so they're wanting advice on a term that's accurate to describe themselves while also being suitable for a child since teaching their kid about the finer points gender/pronouns would probably be a little difficult at this point.