I would suggest a different program for your day #3: either taking an all-day tour from Santiago to Valparaiso, including a visit to some vineyards in Casablanca valley, or just going to Valparaiso for the day. Valparaiso is only 90 minutes from Santiago and it is a completely different city. Valparaiso has a romantic style with all its narrow streets and stairs running up and down the hills that surround the bay, without forgetting the elevators and the incredible houses on the slopes of the hills. Very interesting and singular place, so don't miss the opportunity of going there.