I think each heart in the bottom row needs to be moved one light block to the right. If you do that, they'll be just right, I think.

How about just on the light squares on the outside row - top, sides and bottom?

How about placing a heart in a white square and then the next square embroider a redwork heart of the same design and alternate all through the quilt....I counted 20 hearts and 40 white squares...so should work....and it will look balanced and intentional.

just my 2 red cents worth...

How about starting diagonally with the middle row placing a heart on every other white block. Then work the top rows and then the bottom. I think that would look good.

I kind of like the first one but in the beginning I liked the second one. They both are actually great but still maybe #1

I like Lacelady suggestion too!

What came to mind when I looked at the two pictures was to perhaps start at top left square and place them on the diagonal. Skip a diagonal row and place the next group on that diagonal. If I counted correctly, you would need 19 hearts and you have more than that. So it might work.

The top is done, people!!!

You might try clustering the hearts in the center of the quilt and then the the outer rows become sort of a border around them. They seem a little too scattered to me as they are here. Just an idea.

I love hearts and especially in quilts. The hearts really do add a lot of interest. I'm sure your nephew and his wife will love it no matter where you place the hearts!