bb, plenty of Grandmothers-to-be host baby showers for their daughters! There is absolutely no ettiquette against it. Actually, most of the time, it is the grandmother-to-be who throws the baby shower. Sometimes best girl friends do it, but it isn't considered a "must do", at all. I think you might be confusing the ettiquette of wedding showers with baby showers. Wedding showers should be held by the maid(matron) of honor.
So, move forward with it! Revel in your joy at being a new grandmother! Have fun!
Oh, and Congratulations by the way.
