Quilt them!
Since they are family heirlooms, if quilted they'll be used and displayed. As unquilted tops they'll be stored and be passed down and maybe not appreciated. Much more "valuable" quilted and on display.
I've quilted vintage tops on the longarm that dated to the 1920's without any problems besides an occasional seam repair. I even quilted a top that had some hand-quilting started and we decided to leave the hand-stitching alone since it was part of the legacy of the quilt.
Since vintage quilts are dated from the "youngest" element (whether it's the newest piece of fabric in a finished quilt or the date the actual quilting stitches were finished) that dating affects the value if the quilts are sold. A quilt finished in its era is more valuable (retail) than one machine quilted today but pieced in the 30's.
But your quilts are "family" and won't be sold--so finish them, wrap them around you and enjoy the hugs from your ancestors!
Anne from Guam reacted to ffq-lar in quilting inherited tops?