Congratulations! Can a grandbaby have too many quilts? My great granddaughter is 2 1/2, and has a bunch of quilts. One with the alphabet appliqued on it. One has dolphins leaping (Javahousequilts.com). One has turtles on it. One is just pretty and feminine. I'm working on one with cars and trucks appliqued on it for her baby brother who is about a month old. I also made her some bibs, a diaper bag, a changing pad.
Will you find out the sex of the baby? That makes choosing fabric much easier, but you can make generic quilts until the birth and then do special ones.
I made a quilt for a friend's granddaughter and presented it at a shower. When mommy said something about tucking it away so nothing happened to it, I directed her to read the label which assured her that the quilt was to be used and could be washed if (when) it got dirty.