I'd be surprised, given that Charles Darwin's 'gospel' has long been replaced with more up-to-date scientific discoveries. I would have thought all atheists today would already know that. Anyway, for this hypothetical situation, I would welcome the atheist in and get the kettle on and hope to spend a good hour or so discussing what 'good news' (i.e 'gospel) is regarding evolution, compared with the good news about what Jesus has done for us.
I would hope to share some thoughts by a scholar who examined the question of evolution and saw that there is a truthful aspect to it, a genuinely scientific truth about the way life 'works' on Earth, but that most people have swallowed the myth of evolution which is not scientific. Let me explain by quoting what he said in the book below:
"There is a need to differentiate between the popular evolution that is myth, and the real evolution of the biologists. The current evolutionary theories of scientists may yet be shown to be a less satisfactory hypothesis than was hoped 50 years ago, but that does not make it a myth. It is a genuine scientific hypothesis that arose after many observations and calculations. But this biological theorem must be sharply distinguished from popular evolutionism (Developmentalism) which is a myth based on imagination."
In a nutshell, way back in the 1950s, Lewis pointed out that although genuinely scientific hypotheses about life on Earth often become outmoded due to better, more scientific theories being established, there is another popular belief in evolutionary theory that is just myth. Yet this myth has become established as if it were genuinely scientific when it is nothing but imagination decked out in the 'clothes' of scientific language - to hide the fact that it cannot be substantiated.
The myth of Developmentalism is a myth based on imagination about improvements, whereas scientific evolutionary theory is about changes. Prof. J.B.S. Haldane pointed out that popular ideas of improvements have a wholly unjustified emphasis on changes that supposedly render creatures 'better'. He said, "We are therefore inclined to regard progress as the rule in evolution. Actually, it is the exception, and for every case of it there are ten of degeneration."
I recently watched a documentary by a great proponent of the imagination behind Developmentalism - Professor Brian Cox. He dealt with light and it was all terribly interesting and scientific and there was nothing wrong with it (apart from him crediting blind, mindless universal laws for the way light 'works', and not the great Law-maker who planned it that way). But the week before he had another documentary that was pure imagination as to reasons for developments, biologically. The Great Myth he upholds has imagination dreaming up ideas first, then looking for some scientific evidence to make them acceptable to the general public, who have a great love of myth and imagination.
I would suggest to my atheist visitor that we should use our minds a lot more than does the general public when it comes to differentiating scientific evolutionary theory from the Great Myth of Developmentalism. We need to be up to speed on the way society is being manipulated by documentaries and the Internet to get us swallowing this Great Myth, which is what all current debate is about. This should prevent us from throwing the baby out with the bath-water
If you (or my hypothetical atheist visitor) wanted to explore a good Christian explanation of the need to make this difference, read the paper "The Funeral of a Great Myth" in the book below.
Christian Reflections by C.S. Lewis, pp110-123 (Collins, December 1988 edition)