Oh, I was still working on my response to you...
So here goes..
I am looking a little closer at the first one and it would be easier if I could see it in person. But, some of the fabrics in the first quilt could date to the turn of the century, around 1900 - 1910... So, I think it was made in the 30s propbably with fabric from her stash.
The second one is a little less common from a pattern standpoint as it is more difficult to piece. It is later than the first.. but a nice design.
They are never going to be more valuable on the market than they are to you personally. I think it is very special to have quilts made by your own family member. Nothing is more valuable that than.
And I would finish them.. As to backing, quilts of this period often used muslin as a backing and it works quite well today. As a matter of fact you can get 108 inch muslin backing that works up very nicely. My preference when doing these is to use a cotton batting.
Here is a link to one that I did for a friend.. her blocks were 1900 fabrics..
http://www.myquiltfabric.com/RhondasQuilt.html
Let me know how it works out...