@Debora:
1. I have a argentine wife plus kids, one born here.
Yesterday, the Migraciones guys (whatever happened to Argentine bureaucracy! Young, friendly and dynamic guys in their mid-20-to-30s!) didn't even look at the kid's birth certificate or DNI. The Argentine marriage certificate was all they looked at. "And the kid??" I asked. "No, we don't need it."
2. I am pretty sure that the "antecedentes penales"/background check from your home country is non-negotiable. Even with my Argentine family, they wouldn't touch my papers the first time I went, because I didn't have the foreign background check.
@ndjc:
They did not keep the marriage certificate, but I needed to bring a regular photocopy of all pages.
If it is of any interest, this is the pile I brought yesterday and breezed through (maybe I overkilled, but at least it worked!):
-One passport photo (anyone want another? I have 5 left)
-Passport with valid entry stamp
-Legalized (here in BsAs) translation of my passport
-Regular photocopy of all pages of passport (even blank ones, which were thrown away)
-Legalized transcript of marriage certificate
-Regular photocopy of all pages of the marriage certificate
-My wife's DNI
-Regular photocopies of all pages of my wife's DNI
-Antecedentes penales (from the Piedras 115 office! A breeze!)
-Antecedentes penales from home country legalized abroad, apostille translated and legalized here
-Birth certificate with apostille but w/o local legalization (birth certificate didn't seem essential, I was told it was not needed)
-Utilities bill in my name, could apparently be substituted for a Certificado de domicilio, which should be easy to obtain at your local police precinct.
Good luck!