Yep, they need to sign with the proper pens otherwise someone will use their ball point pen and it will mess up your quilt.
Also it is helpful to make a template cover so that they will only sign in the box and then you will have enough around the signature for seam allowances.
Not sure I'd try it unless I had the money to fund it. Is there a competent family member in each area of the country who could be in charge of getting the signatures for you?