I know nothing about autistic children, but I wonder if something like the "fiddle" quilts I made for Alzheimer's patients at our local nursing hone might be appropriate. I made a lap quilt out of fabrics of different textures and added pockets to put things in, a button that could be buttoned and unbuttened, some velcro, and a zipper to zip and unzip. I even added a string of spools (like beads). I didn't use actual beads because they could be swallowed if the cord broke. Just an idea.