I don't know that they contribute to the gender imbalance - although in fairness the women who make it as far as adminship and discussions on Jimbo's page tend to be unusually thick-skinned (I mean it as a compliment!). I think that the puerile proposals being bandied about are likely to make Wikipedia look like it's run by, well...juvenile geeks who haven't got past giggling every time they hear someone say a "bad word". It would be different if these things were actually funny, but they aren't.
Although I think it probably says something about the general mentality of a significant portion of our editorship what was being proposed for April Fool's day - sex, body parts, and swearing. Hmmm.