Patagonia
Torres del Paine National Park (Parque Nacional Torres del Paine) - Torres del Paine has more cloud ripper mountains than you can imagine. The park, a Unesco Biosphere Reserve, has rugged peaks that tower over pristine lakes. With your kids, you could spend days exploring this park, either on foot, or with pack horses. The wildlife is spectacular - herds of the llama-like guanacos and rheas (like ostriches) as well as the sensational Andean condor.
For hiking, there are well marked trails - you can take a short walks, or if you are more ambitious and want to do more than a day hike, there are hostels (refugios) where you can spend the night (meals are available, hot showers and bunks). Tour agencies will also arrange hiking trips.
Grey Lake (Lago Grey) - Grey Lake is a "must see," not only because of its pristine, blue waters, but who can resist wading in the water with icebergs floating around. Pull out ice chunks and carve them into shapes. Or take a boat to the Grey Glacier at the end of the lake. Guides will take your family (older children) ice climbing on the glacier.
Even in the warmest months (January to March), the weather in Torres del Paine is very changeable, and can be rainy and windy.
Punta Arenas - Punta Arenas on the Straits of Magellan was quite an outpost in the 19th century. In the center of town, at Plaza Munoz Gamero, check out the statue of Ferdinand Magellan, the hot shot who circumnavigated the globe. And climb to the top of Cerro La Cruz, a hill from which you'll have a spreading view of the city and the Straits. The Museo Regional Salesiano Mayorino Borgatello has a great collection of stuffed animals from the region and indigenous Indian artifacts. If you want to see what it was like to be a pioneer in Patagonia, visit the Museo del Recuerdo at the Instituto de la Patagonia - there are old horse drawn carriages and a typical cabin. The Municipal Cemetery (Cementerio Municipal) is worth a stop - huge topiary trees and imposing mausoleums of the founding pioneers of Punta Arenas.
For day trips, to see the Magellanic penguins, take a boat trip to Magdalena Island (Isla Magdalena), or visit the Otway Inlet (Seno Otway) penguin colony. To set foot on Tierra del Fuego, take the ferry to Porvenir (three hour crossing).
Milodon Cave (near Puerto Natales) - Milodon Cave (Cueva del Milodon). In the late 19th century, Captain Eberhard found bones and fur of a long extinct giant ground sloth. The cave has a picnic area and in front of the cave is a huge plaster statute of the milodon, rearing up on its hind legs.