Why aren't you considering Peru? It offers many great adventures and wonderful food. Just a suggestion.
Once you decide where you're going, check back and you can get lots of suggestions about where to visit. For example, I would agree with Eastbay1K that 5 days is actually a fairly long stay in Santiago, but if you're interested in a wine tour, a port tour, a trip to an eco-resort (horseback riding, hiking, white-water rafting), etc., there's lots to do and see in the surrounding area.