Tricky question.... I dont know what the "by the book" rules are, but in my experience these cases are more about how you manage to "sell" your specific situation to the gate agent that checks you in at EZE. Its probably good to check with AA (call their 800 number) and ask for the rule details on what you will get as baggage allowance. If the rules are bad news, then I think you still have a decent chance to sweet talk you way out of getting charged extra at EZE, provided you smile a lot and explain your situation nicely and ask for understanding.