I just make the quilts. I don't ask anyone what they want because then it becomes a contract and the gift gets lost.
If I know boy/ girl I will make appropriate selections. Other than that, they get what I make!
I agree with QuiltnNan, Nancy - I too like the idea of a two sided quilt....using the kids colors on the back and the mom's on the front. !!!!! I will remember this though if I ask someone what they want....would probably mean going to the store for new fabric and not what is in my stash. Good luck.
You did ask her what she wanted so I think that is what you should go with. There are some nice gray and black prints out there right now. As maybe some of us don't like it, you do have to put it in perspective - if your hubby asked you what you wanted for your birthday, you then told him exactly what you liked, then bought you something totally different, would you be satisfied?
Look at it as a challenge that is out of your comfort zone, but not a huge project.
The log cabin idea is a good one. I saw a crib quilt recently in grey and white gingham, white and citrus yellow which looked fabulous. It was very simple with the gingham used for an appliqued shape and the name of the baby, plus one border and the bright colour also used as an internal border.
An Amish type of quilt used black as a thin border around colored squares and as links between the squares with a strong blue as a sashing; that was interesting too.
Babies like looking at geometric patterns and black, white and gray can be an exciting combination so I wouldn't worry about it not being a traditional combination. All the quilts I have made for babies in our family have been used as play mats anyway as small babies often don't have quilts in their cribs.
You can get good ideas about what modern mothers like by going online to the upscale baby store sites and seeing what the current top sellers are.
Good luck with whatever you choose to make.
This could be adapted to grays and blacks instead of whites and blacks -