Hi there,
03/10 to 06/10: Flight to Puerto Madryn + visit to Península Valdés + return to BA on 06/10 or 07/10
If I may, why go so far in such a short time? If it's for the wildlife, I’d suggest another option that doesn’t require taking a flight: the Esteros del Iberá.
Located in Corrientes Province, so relatively close to Iguazú Falls, the Esteros del Iberá are the second-largest wetlands in the world (esteros = marshes), making them somewhat of a small "Pantanal." It’s the country’s largest natural reserve, protecting an incredibly rich biodiversity: Yacare caiman, marsh deer, capybara, armadillo, rhea, otter, and countless bird species, many of which are endemic. Canoeing trips are a real treat. The only places I’ve seen such a concentration of wildlife are in East and Southern Africa.
The advantage for you is the location of the Esteros, between Iguazú Falls and BA. The challenge, I’ll admit, is getting from Puerto Iguazú to Mercedes, the gateway to the reserve where most accommodations are. You’ll need to stop in Corrientes. But overnight buses are very comfortable. From Corrientes to BA, the buses are direct.

The capybara, the world’s largest rodent and an iconic species of the Esteros

The southern screamer, one of the 250 bird species

The Yacare caiman