I would definitely complete the quilt and present it to the parents. Perhaps on the label you could make a statement like..........
One in your hands, One in God's"............
I also know of young parents that gave birth to twins and sadly the one died just 10 short days later. Both Mother and Father were grieved by the fact that no one mentioned the twin that had died. Yes, they grieve but they also want to celebrate the birth of and lives of both twins.
Please finish Noah's Ark.