I would be put out if someone knew the gender and I didn't.
Usually, if the parents know the sex, a shower invite includes the gender of the baby so everybody can buy gender specific gifts if they so choose.
I'm really not getting why you're not telling everybody what your baby is. I don't want to be offensive, but it sounds a little attention-needy. And it's causing a LOT of drama. So much drama, in fact, that I'm not going to bother with real advice. Well, okay, my advice is to TELL EVERYONE!