My first suggestion is to soak them overnight in hot water and some BIZ, then wash without detergent in the washing machine (there's plenty of cleaning agents remaining in the wet sacks) I have found a good Biz soak of old linens removes accumulated dust and debris and softens the harshness out of the fabrics. And no matter how clean Mom's house was these old fabrics have dust and debris.
1. Maybe your Mom was saving the light colored ones for dish towels. You could do some embroidery work on a few and keep them for yourself.
2. Stitch blue work designs (matching the the blue in the colored sack) on some of the plain ones. Use the blue to surround the blocks either with sashing or alternate blue fabric block and stitched block, then use other plain pieces for the backing.
3. Find some old feed sack fabric to complement what you have to make the quilt larger or use the blocks made from blue and plain sacks as a central focus and use add new 30's fabrics for blocks around the center. This keeps your special fabric the focus of your quilt.
Cleaning out a parent's home is a daunting task. Trying to decide what to keep, what to give away or just get rid of is such an emotional experience. Been there, done that.