Fair enough re the Antarctic treaty, but what about colonization of other difficult habitats here on Earth:

-- the Alaska/Canada arctic, and Greenland
-- Atacama desert, or Namib desert
-- Seafloor, even on the continential shelves (tough, but still easier than a Mars colony)

You do of course see some settlements in such areas, but almost exclusively limited to small populations directly engaged in mining, fishing, oil extraction, etc. Also for military and scientific research facilities. How many people would be living on Alaska's north coast if not for oil?

So long as the cost of travel to Mars remains large -- and even cutting it by a factor of 100 it would still be "large" -- I very much doubt we'll see anything but small research outposts unless there is some extremely profitable activity to be conducted there, that can not be done robotically.

And unless those outposts are 100% self-sufficient, I doubt you'll see many babies raised there. So long as more mouths to feed, clothe, and heal on Mars increases the resources that have to be lifted from Earth, or diverts resources away from profit-making activity (e.g., company doctors dealing with sick kids instead of getting dilithium mining engineers back to work), then it's doubtful that such outposts would welcome kids. A couple having a baby at McMurdo station wouldn't be allowed to stay in the antarctic, or on an oil driling rig for that matter, not only because of the treaty or because we don't think it's good for the kid, but because the U.S. government wouldn't want to divert expensive resources into caring for children at its Antarctic research station.

Now, if you have cheap interplanetary transport and technology that allows you to build self-replicating machines (i.e., regolith shoveled in one end, hab modules, drilling equipment, or another regolith converter out the other), then that makes it easy. And maybe we will get such tech quickly; that's more or less the story in Kim Stanley Robinson's Mars trilogy.