They look like a great find. Quilts are dated by the fabric that is in them. They can be no older then the youngest fabric as was mentioned. What you do as far as repair probably depends on your goals. If you are keeping them as a collection you would want to speak with a knowlegable appraiser to determine if repairs would do to the value. If you want to use it, then I would do a new binding just put over the old. Make sure you document what you do and if you find any more information out about their origin.
Congratulations!