What is the primary truth which Catholic social teaching we are expected to bear witness to? First and foremost, it is in regard to man's eternal destiny, which Pope Leo XIII speaks about in his encyclical Immortale Dei:
Nature and reason, which command every individual devoutly to worship God in holiness, because we belong to Him and must return to Him, since from Him we came...The primary truth of Catholic social teaching is that we are not created for this world, but for heaven and God. St. Paul teaches likewise when he instructs Christians that while we are in this world, we should not conform ourselves to it. (Romans 12:2) If this is our purpose, then all we do should be ordered towards that purpose, for as Leo XII teaches "the real perfection of all creatures is found in the prosecution and attainment of their respective ends; but the supreme end to which human liberty must aspire is God." (Libertas, 11)
When John Paul II speaks about the "freedom of the gift" in his Wednesday audiences Man and Woman He Created Them, I think this is what he has in mind. If we are made for heaven, how do we best act like we are made for heaven? The only way to do so is through being a gift to others, to use the gifts God has given us for the service of others, especially in light of the family. In this sense, John Paul II was applying this classic wisdom from Leo XIII to our modern times and our modern families.