Biggest No I could ever give...
Mum is English, Dad is Argentine. I lived both here and UK while growing up. In Baires their house is in the south of province, so back in those days there were no private charters like nowadays and I used to take the lovely Sarmiento train all the way from Temperley to Constitucion to get down town and trust me unless you are all willing to get on taxis every time you have to go somewhere and be back before it gets dark, you don't want your family down there.
I'm pretty sure she thinks otherwise as I'm sure she lived there most of her life and many people know her, so certain street codes apply here.
Reasons you could give?
You'd rather be all closer to "tourist" spots in the city, plus you don't want to be an inconvenient for her nor interrupt her privacy since you will all be coming and going any time of day constantly.
That particular zone of Constitucion is "zona liberada"< "No Man's Land" (area of the city where police do not do their job or are just "freed" from their intervention)
h34r: