Perhaps use the dress fabric in a 12-inch in a star block or other pattern that works well as a single block. Add a border and backing in other fabric and make a small pillow. I wouldn't worry so much "their" personalities...this is about a memory, not a decorating style.

Sorry for your loss.
I was recently looking to make something simple for my niece's first birthday. I bought a small pillow form from the craft store, and made essentially a pillowcase from the bridesmaid dress I wore in her parents' wedding. I accented it with other elements of the dress. It didn't Take too long.

Good luck with whatever you choose.

I think keepsake Christmas ornaments would be perfect, they would suit everyone and would preserve Mom's fabrics rather than use them.

My FIL passed away last summer. He loved his plaid shirts so I made 15- 9 patch potholders by cutting up his shirts. I put a loop of ribbon to hang each one up and a tag on the back saying Memories of Grandpa, dates of birth & death & made with grandpa' shirts. These were made for children, grandchildren & great grands. A momento for them all to keep. found the pattern on this Quiltboard last fall.

Fairly large monogram for the wall, or small one for a mug rug.

A few years ago a friends MIL passed away & she had a couple of quilts all the daughters & grands wanted. The quilts were old & very worn, not very useable. I took the quilts & with their permission, of course, made teddy bears for each of them. They were ragged & very old looking, which they were, added some hand embroidery stitches & made beautiful teddy bears. All the girls loved them.

You guys have the greatest ideas, thank you!! I'll get everything made this summer and give them next December. Thank you!

How about a fancy pin coushion

I'm a huge fan of mug rugs, can never have too many. They are functional, pretty and a constant reminder of who made it AND of your MIL