Another "vote" for not sending anything. I'm so very sorry, but as I said to another poster, I believe that no response for such a long time means that your DDs want no contact, at least, for the near future, even if they haven't said so in words. In fact, your DDs may see any gifts sent as "disrespect" of their obvious wish for distance and just hold it against you. It is very doubtful that any gift you send will be given to the GC. Why waste the time, energy and money?
IMO, the suggestions you've been given - a memory box, savings accounts for the GC, etc. - are good ones. That way, you can respect your DDs; boundaries (even if you feel they are unfair) and yet satisfy your own need/wish to do something for your GC at Christmas (same w/ birthdays). Also, later on, if there is a reconciliation w/ your DDs or w/ your GC when they are adults, as agnurse says, you'll "have something to give them." And I'm adding, your GC will know you were thinking of them all along.