Since you are already in Santiago, why not take advantage of the lovely city. Having been there many times, the best way is, of course to take a city tour thru your hotel .
Remember that you have to be at the airport at least 2 hours prior to departur. I always stayed at a small European style hotel The Santiago Park Plaza. This hotel knows how to cater to the visitor, not like some of the big chain hotels. They arrange everything for you and it is walking distance to some of the good restaurants.
and most importantly, everyone is friendly from the doorman to the general manager.