I've had quilts appraised as well, and it was definitely worth the price (more than your $50). I would have the wedding quilt appraised, yes, and would give them the original appraisal paperwork and a photo right along with the quilt. The point is not to 'brag' about what it's worth, the point is to recoup the true value in case of loss. That's what the appraiser meant when she said it let the owner's know just how much the quilt is worth.
It's their decision whether to insure it or not, but at least you'd be giving them that option and bringing it to their attention. Otherwise, they probably would never even think about having it insured. It's nothing like giving them a receipt for the gift, btw.