Ushuaia is touristy, not speaking Spanish won't be a problem.
The water is fine, you don't need to worry about bottled water unless you're overly worried. You also don't need to worry about a malaria medication.
Cash wise, when I was there you could only get ~$150 out of an ATM at a time and that came up with a $10 fee so just keep that in mind.
In terms of safety and scams, I wouldn't worry too much in Ushuaia. Buenos Aires you might have to keep your wits about you at times depending on where you are.
Hope your dad is okay.
Fun fact - Ushuaia, while 'the end of the world' in the south, is only 54 degree lattitude. So it's kind of less 'the end of the world' than much of northern alberta and the territories.
One more fun fact - the Canadian government gave Argentina beavers to start a fur trade in the 40s & 50s. Beavers have no natural predators in Ushuaia so they've taken over and are destroying the ecosystem. At one point, there were allegedly talks to send bears to solve the problem since they would hunt the beavers.....