ask her, of course. But I would keep the clothes recognizable. In other words, don't cut them up to use just the fabric. I think i would try to mount the clothing on a block, even if it is 1/2 of a sweater and one sleeve. Or the front of pants with' the waistband, zipper, and pockets but no crotch or legs. Capture a t-shirt with a the logo or cute saying "daddy's little man" etc. But do not wash any of it, before or after. A big part of the memory is the smell of the child's garments and maybe food/grass stains . Bless you for taking on this important project.