OK, we did a 6 week driving trip in Chile in 2018 (rent car and Air B&B's).
GREAT trip-- very enjoyable and friendly country. Scenery (vineyards, orchards and view of the Andes) reminded us of the California wine country.
But, assume they will fly into Santiago. Coyhaique is a LONG, LONG way south. We are talking about ferry boat rides south toward Antarctica. WAY off the Chile beaten path.
And driving from Chile to Argentina-- VERIFY! Since Chile permitted England to refuel planes used in the Falklands war against Argentina, do not assume this will be easy. Kind of like travel between Greece and Turkey.
And, yes, though we did not get to the Mendoza wine country, we did enjoy our stay in Buenos Aries, Argentina. But had to fly there, as no rent car company would allow travel between the two countries.