When the blocks were made it was common to use muslin as a sashing. I think I would do that. I have a couple of quilts made by my mom's cousin that had the muslin and feedsack fabrics done in the 40's & 50's.

I would sash them in white, then square them. I would not change any of the blocks she did, leave them as they are, so it remaines her work, Even if they are not perfect, they were hers and it sounds like they want them for a keepsake,

What about putting the same color sashing around all of them. Maybe make it a wide sashing then cut it square but at an angle so that the center sits wonky. I'm sure that there is a name for that besides wonky sashing. I think that would set off each block nicely and disguise some of the uneveness of the original blocks. I think I would use white fabric for the sashing.

not sure what the pattern is called, but add a piece to each side and then cut them out at and angle. this way the blocks will look like they are dancing on the quilt.

ooops, just noticed that the previous poster had the same idea.