I am looking for basic information on the Catholic Church’s position on evolution and natural selection. My son and I have had discussions regarding this and now I have an essay for a class addressing this question. My simple answer has been that the Church does not reject evolution outright as long as it is understood that the creative power behind it is God. Evolution may answer what happened but not why, which is actually the important question. Your answer and other resources I could check would be much appreciated.
What you have said is essentially the Church's understanding of evolution. The Church has said the following about evolution:
Pope Pius XII's Humani Generis:
Teaching Authority of the Church does not forbid that, in conformity with the present state of human sciences and sacred theology, research and discussions, on the part of men experienced in both fields, take place with regard to the doctrine of evolution, in as far as it inquires into the origin of the human body as coming from pre-existent and living matter - for the Catholic faith obliges us to hold that souls are immediately created by God. However, this must be done in such a way that the reasons for both opinions, that is, those favorable and those unfavorable to evolution, be weighed and judged with the necessary seriousness, moderation and measure, and provided that all are prepared to submit to the judgment of the Church, to whom Christ has given the mission of interpreting authentically the Sacred Scriptures and of defending the dogmas of faith.
And Pope John Paul II's Message to the Pontifical Academy of Sciences: On Evolution.
And Pope Benedict had this to say before he was Pope:
We cannot say: creation or evolution, inasmuch as these two things respond to two different realities. The story of the dust of the earth and the breath of God, which we just heard, does not in fact explain how human persons come to be but rather what they are. It explains their inmost origin and casts light on the project that they are. And, vice versa, the theory of evolution seeks to understand and describe biological developments. But in so doing it cannot explain where the 'project' of human persons comes from, nor their inner origin, nor their particular nature. To that extent we are faced here with two complementary—rather than mutually exclusive—realities.
— Cardinal Ratzinger, In the Beginning: A Catholic Understanding of the Story of Creation and the Fall (Eerdmans, 1995), p. 50.