You could mix large squares with blocks made up of smaller squares/strips. If you don't want to mix cotton and corduroy/knit - use them to back the quilt. I have a lap quilt made for my step-dad that's completely made out of double knit and it's the warmest thing in my house. He died over 30 years ago and the quilt still looks new. If you use knits/corduroy as backing you won't have to use batting or maybe a very thin one. Whatever you decide, make sure it will cover your mom from chin to underneath her feet. Ask me how I know.