What a wonderful gift you are giving your aunt and I love the idea of embroidering the names/dates on the blocks. I suggest doing the embroidery just on the quilt top, before you sandwich it. As someone else mentioned, it will hide the knots and it will be so much easier to do a nice job with just one layer of fabric. Without all the bulk of a full quilt you'll be more pleased with the results. I do LOTS of embroidered blocks for quilts and always do them first, then complete the top, sandwich and quilt.
Good luck with this fantastic project. We look forward to seeing it.