Probably you will find a little truth in all the positions you've read. No place is perfect!
I have been in Buenos Aires for two years, plus lots of experience here before that. This is a megacity. Any megacity has crime. You do need to be careful here. I have had my wallet stolen right out of my purse on the subway, and they had to unzip the purse while it was hanging on my shoulder. HOW did they manage it? I have no clue. They actually have conventions here (the petty criminals) with contests and so on.
But I learned. I have a purse now with a flap that folds down over the zipper. I STILL had someone try something but I was now wiser.
Also there are many frustrations. If you are used to a country where efficiency is the rule and customer service, prepare for a change. It does wonders for your patience if you do adjust to it.
And yet many things here are wonderful. I have been here two years and I like it. I do not live in La Boca. That would not be wise. Nor in Constitucion. I like San Telmo. It is the historical area of BA with very old buildings, etc., but was told for a woman my age not to stay there. It is borderline. I live in Palermo in a very safe area. It is beautiful, I have good neighbors, I like the neighborhood, the storekeepers. I like everything about it.
But if I had had some bad experiences, perhaps I wouldn't say that. I know one woman here who was knocked down on the sidewalk once by three men who stole her shoes right off her feet. They were expensive high heels. It has not happened to me.
I think it's important to live in a good area. Since you already have a job opportunity here, that's the best. A business here, from all I hear, can be difficult with a lot of government interferance. I don't have experience with that though. It's what I've been told.
I hope this helps. I think attitude might have something to do with it too. It is easy to get frustrated with the negatives. But I am from the US and when I go back, I find things I don't like there as well. I'm from Brevard County, Florida. If you are friendly to someone in line at the grocery store, they will act like you must be up to something. Here in Buenos Aires it's entirely different. I've been standing in line at the checkout before and had someone from the rear of the line walk up and give me a handfull of % off coupons to apply to my bill. She had more than she could use and she didn't just throw them away.
Lately I fell in my apartment. Thought my arm might be broken. I knocked on the neighbor's door (I've been here 2 years and had not met him, he's a young guy I learned who works in movie production here). I asked him where there is a hospital I could just check to see if it was a fracture. He looked at it and said, "It IS broken (it wasn't but it had swelled quickly) we are going to the hospital. I said "That's okay, I'm fine, I'll take a taxi (they are very cheap here). He said, "No! I'm taking you. We are going in my car." And we did. He took me inside, made sure I was where I needed to be (to wait), left for a few minutes, then came back and gave me 20 pesos just in case I didn't have small bills and the taxi home had a driver with no change. Of course I paid him back the next day.
This is just a bit of my experience here, both good and bad.
I think if you just ask someone who has experience here where to live and for some guidelines, it will be good for your girls. I don't intend to go back to my country, if that tells you anything.