Hi Megan,
I'm so very sorry to hear this news. What a lovely thing to do for your Sister. We are honoured that you chose our design.
I agree that white fabric and stitching it all will look great. We have a finished picture of this one in our gallery on our Artecy Cross stitch website. It looks stunning once stitched.
On 14 count, when stitching with black cotton, sometimes with two strands the white fabric can show through a little. I personally stitch on 18 count for this reason as I think it gives better coverage with two strands, especially if there are alot of dark colours in the design. You can do a test on a piece of 14 count fabric to see if you are happy with the coverage with just two strands, you may wish to use three strands instead. Alternatively I have heard, but not tested myself, that anchor black cotton is slightly thicker than DMC black cotton, so some of our stitchers use anchor for black instead. Hope this information helps and you enjoy stitching this design and are happy with the results.
Best Wishes to you and all your family.
Tereena
Artecy Cross Stitch