Oh Grannie314 so many other grannies have the opposite situation - no contact with loved grandchildren because of divorce. Its sad the "other" GP have withdrawn, but we never can really know what went on to bring this about due to the dynamics of the divorce.
for example - supposing it was you ex SiL intervened and insisted? Unknown to your DD?
You're right..hang on in there, talk to the grandchildren as if they are a reality, but that there has been hurt and give it time, etc etc if they ask xx