the sweatshirts are not good candidates for raggy---they will not rag the way a rag quilt does.
a t-shirt style quilt would work though-where you use the motif's designs of the sweatshirts= i would use a backing and probably either a very lightweight batting, a layer of flannel or muslin, or no batting at all-depending on how warm you want it-
another good way to use the sweatshirts is to use them to make quilted jackets- then you can (wear) a piece of your mom---
my sweatshirt jackets always get compliments when ever i wear one- people just love them- and they are easy, fun to make....you could make a variety of designs/colors/styles to go with many peices of your wardrobe. also vests.
do a search for quilted sweatshirt jackets to see many