I fell into this same situation. I knew my sisters were going to throw me a shower, just wasn't sure when. I'm due January 10th. by the middle of November I was a bit concerned no invitations had gone out or a date even selected since the holidays would be thrown into the mix. So I just called one of my sisters and just asked if anyone had made any decisions. In my family, I'm the party planner so they honestly were not sure where to begin. I just told her someone just had to nail down a date and get invites out, the food and everything else would fall into place later. So she did, by the end of the day she had talked to my sisters and they selected a date and the next weekend invitations went out.
I felt bad poking my head in, but I also knew they just are not as organized as I am.