Authentic joy is based on this foundation: that we want to live for God and want to serve others because of God. Let us tell the Lord that we want nothing more than to serve him with joy. If we behave in this way we shall find that our inner peace, our joy, our good humour will attract many souls to God. Give witness to Christian joy. Show to those around you that this is our great secret. We are happy because we are children of God, because we deal with him, because we struggle to become better for him. And when we fail, we go right away to the Sacrament of joy where we recover our sense of fraternity with all men and women.[Alvaro del Portillo, Homily, 12 Apr 1984; quoted by Francis Fernandez Carvajal in In Conversation With God, vol.5, p.155]
There is no direct reference to GKC in the quotation above; Bishop Portillo does use the same language as Chesterton to talk about joy. Many people were — and still are — lead to God due to the peace, joy, and good humour shown by Chesterton. Also you noticed (how can a reader of GKC not notice?) that Portillo referred to joy as "our great secret."