You can mix the fabrics if you stabilize the knits and the flannel with an iron on stabilizer. If you use any new fabrics for sashing etc. be sure and wash it to make sure it doesn't shrink or bleed. It is going to be hard enough to put this together without trying to make a specific pattern. Start with the largest motif etc. that you want to include and size everything else to go with it. It would be nice if you could photo tranfer a picture or pictures of the deceased on to a block in the quilt. It would be nice if it was the center. Such a project can be frustrating but it is a labor of love for most of us.