I would maybe do something less overt than making heart blocks - maybe a plain design in blues, but then include a couple of hearts in the quilting?
Also, when I made a blanket for a grieving couple (after a miscarriage), I gave it to the mother and told her that if she felt that it wasn't something she wanted to keep - if it would be a painful reminder or if she didn't want it for any other reason (and she did not need to justify herself), I would donate it to a NICU in honor of the son she lost. In her case, she was honored to receive it... but if you feel it is appropriate, perhaps you could have a relevant charity in mind that you could donate if the family is uncomfortable with your gift.